Deviating from watches for a quick second

Instead of profiling another watch this week, I thought I'd share something I think is kind of cool. I'm still very much infatuated with the Citizen eco-drive watch I bought last month, so in my spare time, I did a bit of research on it. Being a tech-guy, I was interested in how, exactly, the watch worked (in terms of the radio control, as well as in terms of the "eco-drive"). Being a patent agent, I figured the easiest way of getting more information was to search the US patent database.

Turns out Citizen has a crazy amount of patents on both the radio control mechanism and the eco-drive mechanism. It's insanely complex stuff - everything from where the solar cell is located, to the placement of the radio antenna within the case, is patented. Reading these patents, it's amazing how much time and energy went into this technology. Everything has been considered.

The claims are quite interesting. For example, US patent 7,372,779 is an issued US patent, with the following abstract and first claim:

The invention is directed to obtaining a radio controlled timepiece that, in a case when the user who uses it moves from one country or one region to another where the time difference is different, has simplified an operation of correcting the time difference between the countries or regions and an operation of correcting the time difference due to daylight saving time's being executed. To this end, the invention provides a radio controlled timepiece 1 that, in addition to the radio controlled timepiece 1 in the prior art, it further includes offset time difference information storage means 8 that stores an offset time difference between a country where reference time information is formed and a country where a standard radio wave has been received and daylight saving time information storage means 9 that has stored therein for future use information on whether daylight saving time is being executed in the region where the standard radio wave has been received, and local standard time information forming means 10 that, with respect to the reference time
information of the standard radio wave that has been received in a particular region, executes calculation processing by using at least either one of offset time difference information with respect to the reference time information corresponding to the particular region and daylight saving time information in the particular region, to thereby form local standard time information in the particular region.

1. A radio controlled timepiece, which comprises: a reference signal generating means that outputs a reference signal; a time keeping means that outputs time keeping nformation based upon said reference signal; a display means that displays time nformation based upon said time keeping information; and a receiving means that receives a standard radio wave having time information, whereby output time nformation output from said time keeping means can be corrected based upon a reception signal output from said receiving means, and wherein said radio controlled timepiece further comprises: an offset time difference information storage means that stores an offset time difference formed between a certain region and a particular region where said standard radio wave has been received, by setting a time information in said certain region as a standard time information; a daylight saving time information storage means that stores therein information whether or not a daylight saving time is executed in the region where said standard radio wave has been received; a local standard time information forming means that executes an operational processing by utilizing said offset time difference information formed between said time information of said standard radio wave as received in said particular region and said standard time information, and said daylight saving time information used in said particular region, so as to form said local standard time information in said particular region; and a time difference correction history information storage means that stores information on whether or not a user has manually corrected time difference information, and wherein said radio controlled timepiece is configured so that when said radio controlled timepiece has received said standard radio wave, said offset time difference of said offset time difference information storing means is adjusted by utilizing said information of said time difference correction history information storage means, said daylight saving time information stored in said daylight saving time information storage means as obtained when said standard radio wave has been received at an immediately preceding sampling period, and said daylight saving time information as obtained when said standard radio wave has been received at the present sampling period, and then said local standard time information of said local standard time information forming means is adjusted based upon said adjusted offset time information and said daylight saving time information as obtained when said standard radio wave has been received at the present sampling period.

Based on the abstract, it looks like my watch is covered - the time is automatically calibrated for the time zone and daylight saving time information received. However, I'm not sure whether the watch falls under claim 1 (not sure I have a "reference signal generating means" on my watch).

US 7,408,845 seems more on point:

1. A radio correcting timepiece comprising signal receiving means for receiving plural standard radio waves having time information and timepiece means for correcting time operation to display time on the basis of the time information contained in at least one standard radio wave received by the signal receiving means, wherein: said correcting time operation operates to receive said time information according to a predetermined receiving order for each standard radio wave, and in the case of success in obtaining said time information from either of said standard radio waves or in the case of unsuccess in obtaining said time information from all of said standard radio waves operates to terminate said receiving operation, and, further in the case of said success, operates to correct the time based on the time information obtained, and, on the basis of the information related to success or unsuccess in obtaining said time information from one or plural standard radio waves obtained by said correcting
time operation operated in the past, said predetermined receiving order of each standard radio wave used in said correcting time operation after the past time is renewed.

But the coolest are the design patents. US D554,536 definitely covers the design elements of my watch, though I guess you'd have to have all of the designs to be confusing... If they really wanted to cover it, they would have separate design apps for the different "portions" of the design - the slide rule, the face, the hands, etc.:

It's kind of cool. And Citizen, (or Swatchgroup, or anyone else) - if you're looking for someone to file your industrial designs in Canada, let me know - no one else will be able to convince the Canadian Patent Office of the distinguishing elements of your design better than me!

Citizen Skyhawk

This week I'm taking a break from the Diver's watch segment (I know, I know, after only two segments! We'll get back to it next week, promise). The reason is that I recently aquired a new watch, and it needs to be written up.

As you may have noticed from earlier posts, I have a thing for atomic watches. That is, watches that can receive the radio signal from the US military atomic watch (which is, I think, in Boulder, CO) that is used to synch satelites. The appeal of these watches is that they tell the "perfect" time. Well, till now I had one (the red faced Casio). It's a great watch, but not the most appealing from a esthetic point of view. I've been meaning to upgrade it for a while.

So I've had my eye on the Citizen Skyhawk series for a while now. These are probably the most upscale of the Citizen sports watches. The one I bought looks great, and has an insane amount of features.

Like the Casio, it's Atomic. But unlike the Casio, it can receive the radio signal from four different atomic clocks: the one in the US, one in Europe, and two in Japan. It chooses the right radio signal automatically, based on the time zone you tell it you are in. It listens for the radio signal three times a day - at 2, 3 and 4 am, where atmospheric conditions are optimum) and automatically adjusts the time and date (both the hands, and the digital face) accordingly. You can also set it so it receives Daylight Savings Time information from the atomic clock - so you never have to worry about that, either.

You can also ask it to synch at any time, by pushing a button. This doesn't work too well during the day, since it has trouble receiving the signal. And if that's not enough, you can change the 4am synch time to any other time you want.

The watch has so many additional features, I've got to use headings!

Eco-Drive

This is an an "eco-drive" watch, which is the trademark for Citizen's solar technology.  Citizen was probably the first watch company that used a solar panel that doesn't look like a solar panel.  On this particular watch, you can't tell there's a solar panel at all.  I think the whole face is a solar panel, but it looks just like a normal, black watch face.  It's quite amazing to me that the solar panel is so efficient - there is very little real estate on the watch dial, what with all the markings, hands, lcd screens, and all.  But if you look at it closely, you can sort of tell that the solar panel is there - the dial isn't quite black, seen under strong light, it's a bit of a translucent gray.

The solar panel charges a capacitor.  The advantage of using a capacitor instead of a rechargable battery is that, in theory at least, the capacitor will never need to be changed, and the capacitor can be charged and recharged ad infinitum.  A rechargable battery only has a certain life span, and a certain number of charges.  Apparently, the watch also has a back-up battery, but I'm not sure how power gets allocated. 

All in all, this must be pretty sophisticated technology - a capacitor isn't normally very good at giving a slow trickle of energy.  The solar panel would need some kind of "cut off" so you don't over charge the capacitor or the battery.  There needs to be some kind of switching from capacitor to battery, when the charge gets low.  Lots of circuitry.

Apparently, at full charge, the watch is good for 200 days.

The solar panel allows the watch to "know" when it's being used, and Citizen has used this to its advantage in a really clever way - if the watch is locked up in a drawer for longer than a certain amount of time (i.e. if the watch face doesn't see any light at all for a certain amount of time), it goes into a hibernation mode.  There are actually two levels of hibernation - for the first, the watch shuts off the digital display.  For the second, the watch hands stop moving (but the watch still 'remembers', or counts, the time).  The minute the face hits a bit of light, the watch "knows" it's in use again, and the hands jump to the correct time.  Really, these guys have thought of just about everything.

The neat thing about this technology is that, really, you never need to open the back of the watch.  The watch back actually says "do not open! service center repair only".   The only time you would ever need to open the watch is if it broke.  I've never had a watch that tells me not to open it!  Very neat.  I suppose this also makes it easier to get the water resistance where it is (no o-ring worries).

So the battery never needs changing, and the time never needs adjusting. Talk about a low maintenance watch!

Titanium

The Skyhawk comes in stainless steel, a blackened stainless steel, and titanium.  The one I bought is titanium.  Says so right on the dial.  I tried on all three, and the titanium one is remarkably lighter.  The watch face is still fairly heavy (I guess all the electronics inside can't be too light) but the bracelet is about half the weight you'd expect it to be.  This results in a watch that is very easy to wear.

Titanium also looks great, in my opinion - it's slightly different than stainless, with a bit more of a gray tint.

Titanium is famous for being very hard to work with, which is why all the detail on the band is quite surprising to me.  Note that the majority is brushed titanium, but the small links that connect the main links are polished titanium.  This gives a subtle two-tone effect.  Note that not all of the small links are polished - this would make it look stripey, like a Cartier Panthere.  Instead, just the linking links (if you know what I mean), or every second link is polished.  Very neat look.

The clasp is operated by two buttons, one on each side.  There is no wetsuit extension.  A bit disappointing, but I guess this is supposed to be an aviator watch, not a diving watch.

Sapphire Crystal

Of course, the watch has a sapphire crystal.  This is almost standard these days.  I imagine it will be hard to scratch.  There doesn't appear to be any anti-glare coating, though, which is a bit disappointing, I suppose.  

200 Metre Water Resistance

I would have settled for 100m.  50 is kind of weenie - most watches have this, and it doesn't mean much.  But 200m water resistance is serious water resistance.  You can wear this in just about any situation without worries.

Slide Rule

Yes, the watch has a rotating bezel.  And in true aviator watch style, the rotating bezel is one part of a three part slide rule.

The slide rule is actually very useful if you know how to use it.  Multiplication and division are very, very easy to perform.  Apparently you can use it to calculate a square root, but I've never needed to calculate a square root, so I never learned how.  Time calculations are also easy, thanks to the third part of the slide rule.  So, you can calculate how much time you can fly for if you are using 30 gallons of fuel per hour and have 73 gallons of fuel in your tank (just slide the "30" to the 12 position, and look at the time at the 73 position).  Equally useful are the little indicators for commonly used calculations.  I can never remember how many km there are in a mile, so it's actually really nice to see km, nautical miles, and statutory miles actually indicated on the bezel.  It also has indicators for fuel lbs/litres/oil lbs/imperial gallons/US gallons, which I would probably use less (though US gallons to litres might come in handy at some point).  Very cool, very functional - it's like having a metric conversion calculator watch, without all the geeky buttons.

I think the bezel is titanium, painted black with white numbers.  The interior (non-moving) bezel looks like an aluminum, painted black with silver numbers.  A bit wierd to have the white so close to the silver - it would have been nicer if they were all the same colour - but it's hardly noticable, and obviously cost a whole lot less than either painting the aluminum numbers white.

Because the bezel is titanium, the machining on it isn't as perfect as I hoped - it's a bit tough to turn.  But maybe that's by design.  In any event, the twelve round protrusions add both functionality (making it easier to turn the bezel, both with or without gloves on) and interesting style.

Dial

The dial is amazingly cluttered.  Four dials, two LCD panels, a three layer slide rule, 8 hands, hour markers, minute markers, and a whole lot of writing).   Despite this, it looks quite organized and it is very, very easy to read the time.  The main hands are very large and legible in all light conditions. The hour markers are also quite large, and luminous. The minute markers are also larger than on most watches.  

As if this wasn't enough, the watch has an LED backlighting (red, so that it doesn't effect your night vision), though it only lights up the LCD panel (it would have been nice to light up the whole dial).  This backlighting only works in some modes, so if you're using the chronograph in the dark, you're out of luck.

I'm going to go through each of the features of the dial in clockwise order, starting at 6.

Mode dial

At the 6:00 is the mode dial.  This features 8 different modes: starting at 6 again: time, calendar, timer, chronograph, world time-set, alarm-1, alarm-2, and radio control-set.  You change from one mode to another by pulling out the crown one notch and turning it.  This is actually quite annoying - it would have been much better if they kept with the old Citizen system - jsut turn the crown in the standard position, without having to pull it out first.  Citizen probably had a reason for changing this - maybe people were complaining that the mode was always accidentally changing while it was on your wrist. 

In the "time" mode, the left hand LCD indicates the current time zone of the hands of the watch, and the right hand LCD indicates the time for the time zone you've selected as your "world time".  Pulling out the crown one stop enables you to set the time zone for the right hand LCD display.  

In the "cal" mode, the right hand LCD display indicates the day and date.

Timer and chrono features work like on any digital watch, with the features appearing on the right hand LCD.  Oh - one nice thing, in chrono, you get hours, minutes, seconds, and hundredths, all showing.  None of this hundredths disappearing when you start logging hours.

World time set allows you to add or remove different time zones from your scrolling list of time zones in "time" mode, and allows you to set daylight savings time manually.

The two alarms work like on a normal watch, with one exception - you also set the time zone, which is a great feature.  So you can set the alarm to ring at 8:00 am Cairo time.

Rx-S mode allows you to set the various features of the atomic/radio controlled aspects of the watch.

LCD panels

Just below 9:00, and between 3:00 and 4:00 are two LCD panels.  They are used for the various modes/functions, as discussed above.  It's kind of cool to have a dedicated LCD panel that tells you which time zone you are in.

Battery/Radio indicator

At 10:00 is the battery and radio indicator.  In every mode except radio reception mode, it indicates the life of the battery, with four positions.  Kind of like a "reserve de marche" indicator.  Very neat.  I've never seen it anywhere but the "fully charged" position, but I imagine that may change over time.

When the watch is receiving a time signal, the battery indicator hand rotates to indicate which radio frequency it is dialed in to - US, Europe or Japan.  The radio frequency is set automatically based on your time zone, so this is a bit redundant and useless information, but it's pretty cool to have the words "US, EUR, JPN" as settings on the watch - which is probably why they did this.

UTC

At the 12:00 position, the largest subset dial, is the "UTC" dial.  There are two hands, one a normal minute hand (in white) and the second a 24 hour hand (in orange).  This dial always indicates UTC, otherwise known as (I believe) Grenwich Standard Time.  Kind of cool for an aeronautic watch, since GMT is used constantly when flying.  But for me, it would have been much cooler if this was set to the second time zone, for quick reading of that time.

24 hour hand

At the 2:00 position is another dial, with one hand, which indicates the time, on a 24 hour scale.  This could have easily been replaced with a little orange aperture (am/pm) since you already have the time on a 12 hour scale with the big hands.  If they had done this, it would have left room on the dial for an analog view of one of the alarms, which I would have preferred.

As it is, the three dials on the top half of the watch are pretty much useless to me, but that doesn't stop them from being cool.

Radio Signal Indicator

At the 11:00, 12:00, and between 1:00 and 2:30 are indicators for the radio signal.  When the watch is attempting to synch with the atomic clock, the second hand will move to "RX", which is indicated at the 12:00 position.  If the watch fails to receive a signal, the second hand will move to "NO", at 11:00.  If the watch receives a signal, it informs you the strength of that signal by pointing to L (low), M (medium) or H (high) indicators between 2:30 and 1:00.  Very neat.  You can also confirm whether a signal was received by pushing the lower of the two pushers.

All in all, a very nice watch.  A tad complicated, but actually quite easy to use.  

After a week of wearing it, I would make the following improvements:

1) LED lights for the whole face rather than just the LCDs

2) LED lights that work regardless of mode

3) Second time zone indicated at 12:00 dial, rather than UTC (though I'm sure people will disagree with me on this one, so I'm not too fussed)

4) Alarm indicated at 2:00 dial, rather than 24 hour hand

5) Mode dial that works in default crown position, rather than having to pull the crown out to change modes

6) Bezel that is easier to turn

I think you'll agree that these are all pretty minor points.  So far, I'm thrilled with the watch.

The Ultimate Divers' part II - The Rolex Submariner

This week's watch of the week is a little early, since I'll be "computer free" for a while.  I don't have too much time to find something esoteric, and realistically, I couldn't do a search for the ultimate Diver's watch without at least considering the entries from Rolex, so we'll get those out of the way today.

For a lot of people, the Submariner is the ultimate diver's watch, and it's not hard to see why.  It's the watch that everyone else copied.  The oyster case was one of the first waterproof cases, meant for extreme use, and the Rolex is really very functionally and clasically laid out - which is why it hasn't changed too much 

in the last few decades.

I'll be looking at a few different Subs, though, since the devil is in the details, and you can really tell what's important in a watch by the little changes that are made over the years.  All photos used today are courtesy of Antiquorum.com - these are all watches that Antiquorum sold over the last week, in their mega watch auction.

So let's look at this first sub.  Black dial?  Check.  Easy to read, luminescent hour markers and hands? Check.  Unidirectional rotating decompression bezel, with luminescent marker and markings every 5 minutes?  Check.  Easy to turn with gloves on? Check.  Water resistant to a reasonable depth? Check.  Touch crystal and band? check.  So it's a diver's watch.  

But let's look at some of the extra features that make this Submariner so special.  Crown guards.  Nice touch.  This way, the screw down crown doesn't get banged up from hits to the side.  It also prevents the crown from accidentally getting unscrewed (which would be very bad at 300 metres).  

The first 15 minutes of the bezel are ticked off every minute, to make it easier to see exactly where you stand.  There is also a subtle, but readable minute chapter ring on the dial.  The hands are easy to read - the "mercedes" hour hand, called this because it resembles the mercedes symbol, is unmistakably distinct from the minute or second hands.  The second hand is big enough to read easily, but tapers to a fine point for accuracy.  It is perfectly aligned with the minute chapter ring.  The second hand has a big luminescent dot making it easy to read, but is quite thin for accuracy.  Use of a triangle at 12 and sticks of luminescence at 3,6,and 9, with circles of luminescence at the other hour markers, make this watch very easy to read - you always know which way is up.  Many, many other watches have copied this style.

The oyster band has also been frequently copied.  Nice, big, solid chunks of stainless steel.  In earlier models, the band looked pretty much the same, but solid links weren't used - instead, they were thick sheets of metal folded to shape.  This was fine, but as the watches got used and got older, the metal would bend out of shape slightly, resulting in band "stretch".  Not a big deal, since it really didn't effect the integrity of the band, and actually probably made the band more comfortable to wear, but people didn't like this (made the watch look old) so the solid links (which are also purportedly stronger since the links are solid metal) were adopted.  Of course,

 the band is only as strong as its weakest link, and the spring bars are the same, but so much of the watch business is perception!

The clasp (which can't be seen in any of the pictures) is also much copied.  It folds over itself and never actually separates - another safety feature - it would be hard to lose this watch over your wrist, even if the band somehow got opened.

People have gone on and on about the history of Rolex (to me, looks like a beautifully executed "marketing" play from the start, and not really about watchmaking - for a long time, they had other companies make their movements, under confidentiality).  People have gone on and on about the movements (oyster perpetual, has all sorts of refinements, including use of interesting alloys and mechanisms to increase reliability, all are officially certified chronometers, etc., etc., etc.,).  But I really don't know enough about Rolexes to add anything of value to those discussions.  

Instead, let's look at a couple of "variations on the theme", and see where they get us.

  This one is a "sub date".  The biggest difference is that it features a date window.  Personally, I don't like the date version as much, for a few reasons.  First, the date window is magnified by what's called the "cyclops" loupe.  There's actually a big piece of glass (or acrylic, depending on the year of manufacture) that sticks OUT of the crystal.  If I had one of these, this would get banged up.  A lot.  I'd end up with lots of scratches on this piece of glass, since it sticks out and just asks to be banged into something.  Second, I think the big white aperture window detracts a lot from the symmetric nature of the face.  Everything else is black.  Your eye just automatically goes to the magnified (and distorted, since magnification will do this) date, rather than to the time.  Other watch brands have used an inverted date (with the number in white, on a black background), and I like that a little more.  Finally, this is a sports watch.  A diving watch.  I'm going to wear it diving.  Even James Bond didn't wear his all the time - he had a dress watch for dress occasions.  So every time you wear it, you have to set the date.  No thanks.

The other obvious difference between the two watches is that this one looks to be a bit older.  The luminescent markers have yellowed nicely, giving a vintage look.

This next one is called the "Roger Moore" sub.  Not sure why, but I suspect it's the model Roger Moore wore in Moonraker, or some such thing.  

Even though it's got "Roger Moore" in the name, I quite like it.  The luminescent strips have aged quite nicely, and almost look orange.  

A "sub" discussion just wouldn't be complete without a look at the watch known as the "James Bond" submariner.  This is a much earlier version of the watch, made famous for a close-up shot in one of the very early Bond movies (possibly even Dr. No).  Although it's got the submariner rotating bezel, it looks a lot like an Explorer, because there are no crown guards.  Also, I think the overall size of the watch was a fair bit smaller than the submariners you see today.  

It's got so-called "historic value" because of it's movie fame, but I think I'd rather have a version with crown guards.  

If I had my choice, I would get an older one, with a matte dial and as little as possible written on the face (the later Rolexes have more 'stuff' on the face; "superlative chronometer", water resistance in feet and metres, etc. etc. etc.).  Nicely yellowed luminescence (radium if I can find it, or if they ever used it - there's something cool about a radioactive dial).  Crown guards.  And (yes) an acrylic crystal.  None of this sapphire crystal stuff - old school.  I wouldn't care so much about the stretch on the band, or whether the band had a wetsuit extension clasp (some of the newer ones do).  Definitely no date.  This is something I really didn't know I felt so strongly about until I wrote this article - so I guess there is a use to this!  The more I think about it, the more I think a date window detracts from a divers' watch - at least from THIS diver's watch.

I should note that the bezel comes in different "flavours" too - they came out with a "Rolex Green" bezel for the watch's anniversary a few years back.  And I think there might be a few with the first 15 minutes in a different colour.  Oh - and I think the new ones are ceramic rather than painted steel - which means they don't scratch or wear out nearly as much.  But those features are unnecessary to me - a Sub should be banged up - it's a professional divers' watch.  And it should be as black as possible, 'cus that's just the way it should be.

First of the Divers'

OK, I should be working. Or talking about a specific diver's watch. But Antiquorum (www.antiquorum.com) is having their auction this week. I wish I was there. Their online catalog is insane - I've been lustfully leering at some of the watches that are going on the block this week. The Antiquorum fine watch auction is easily the most amazing collection of watches sold in one spot at one time - it's the Barrett-Jackson of watch auctions. There are literally hundreds of watches I'd love to own.

So this week's Diver's watch comes from that auction. It's not something you see every day, and it's a hard core diver's watch. With this watch on your wrist, every one will know you are a diver. If you're wearing this watch without being a diver, you're a bit excentric - it's just so huge, so focused on diving, that people will wonder a bit about you.

The watch fulfils all of my criteria for a diver's watch. The face is black. It has a metal band. It also comes with an original Omega rubber strap, and a spare link bracelet, so you know you're not messing around here. The watch is waterproof to 600 m, which is more than enough for anyone diong diving.

The watch is just massive. It has a huge, easy to read graduated bezel. There's a huge (easy to operate with gloves on) red button for locking the bezel. So if you set the bezel, and push the button, the bezel won't turn, in either direction. No mistakes. The winding crown is at 9:00, which is unusual, and it's heavily protected - look at those massive crown guards! It's also a screw-down crown.

The minute hand is bright orange - you'd have no problems seeing this in any light situation. The second and hour hands are also big and easy to read.

This watch has an automatic movement. Easy to read minute and hour markings. A big, bold, luminescent markign at 12. And what appears to be luminescent markings on the rotating bezel (something I haven't seen before).

This is a serious watch. My only concern is its size 55 mm wide!!! - if you're not diving, this would be awkward, and probably very heavy to wear. It's got that cool retro 70's feel to it, though - you know this watch has seen some interesting sights in its time.

The search for the perfect dive watch

I know it's not Wednesday yet, but I thought I'd start out the week with a new idea.  Instead of random "watch I like" posts, for the next few weeks, I'll be exploring, researching, and highlighting dive watches, in the search for a "perfect" dive watch.

Just about every manufacture of watches makes at least one "dive" watch.  The first that comes to mind for most people is the Rolex Submariner.  Most other dive watches are at least loosely based on the Sub.  But even among Subs, there are all sorts of different styles.  The hands on an older Tudor Sub are quite different from the hands on a modern Rolex Sub.  The dials, and rotating bezels, can be different colors.  And of course there's the "Sea Dweller" - the uber-Sub.  

Other examples quickly come to mind - the Breitling Top-Time (James Bond's had a geiger counter built-in).  The IWC Aquatimer.  The Patek Philippe Nautilus.  The Cartier Pasha.  The Omega Seamaster.  The Seiko and Casio dive watches are also right up there.

So, what makes a watch a dive watch?

Wikipedia defines a dive watch as a watch designed for underwater diving that features, as a minimum, a water resistance greater than 10 ATM, the equivalent of 100 meters (330 feet).  There is an ISO standard for diver's watches (ISO 6425).  These are suitable for diving with underwater breating apparatus in depths of 100 m or more; an ISO 6425 certified watch can be marked with the word "DIVER'S".

But there are thousands of watches out there that are water resistant to 100 m.  Really, you could take just about any modern watch scuba diving.  So what unique features make a watch a diver's watch? 

Well, the ISO certification standard gives us some clues.

1) Fantastic visibility in just about all levels of light.

The ISO certification requires adequate readability at 25 cm in total darkness; an indication that the watch is running in total darkness; clearly distinguishable minute markings.

But a good diver's watch, I think, should go beyond this.  It should be legible at any light.  The sun's glare.  The light of the moon.  A dim reflection.  A lot of watches are readable in complete darkness; it's when there's just a little bit of light that makes reading them difficult - your eyes adjust to absolute darkness, and become much more sensitive.  Analog watches should have several different ways of reflecting light back to your eyes.  The hour and minute hands should have a healthy amount of chemiluminescence.  But they should also have some "mirrored" elements, and (ideally) some sections in white or other color that contrasts highly with the colour of the dial.  Hour markers on the watch should be the same - ideally they should have mirrored segments, black or white segments (high contrast to the face color), and a healthy chemiluminescent dollop.

Although a diver's watch can have a face of any colour, the majority are black with white hands and markers.  I think my "perfect" diver's watch will have to have this color combination, or a minor variant of it (dark blue?).  Strictly an aesthetic thing, but isn't that the most important thing here?  After all, it's not like I even dive!

2.  Easy to read the exact time

The ISO standard states that there should be clearly distinguishable minute markings on the watch face.  Makes sense to me.

3.  Unidirectional bezel

The ISO standard states that there should be a unidirectional bezel, with elapsed minute markings at least every 5 minutes, and a specific marker to mark a specific minute marking.  

In other words, there should be a rotating bezel.  It can only rotate in one direction.  So, once it's set, it can be accidentally moved, but only to tell you you have LESS air, not that you have MORE air.  i.e. if you set the marker at the minute hand now, the minute markings will tell you how long you've been underwater.  If the bezel gets moved accidentally, it can only be in the counterclockwise direction, which means when you see how much time you've been under water, it will seem like more, not like less, time.  

I would add a few things to the ISO standard (not that I've read the ISO standard, but I'm just reading about it on Wikipedia...  my apologies if these things are part of the standard already, and just not mentioned in Wikipedia).  First, the specific marker should be chemiluminescent.  It should also be readily visible in any light conditions.  AT A MINIMUM, you should be able to read three things in any light conditions: the location of the minute hand, the location of the "12", and the location of the bezel marker.

Second, the bezel should have some kind of grip on it, so that it can be easily turned, even with gloves on.

Third, the bezel should "click" every minute (or half minute). None of this free-wheeling bezel stuff - you need a bit more accuracy than that.

Fourth, ideally, the bezel should be designed so that sand and salt won't gum it up.  I don't want to have a "stuck" bezel, just because I've been in the sand or sea - that's what it's for!  I'm a bit torn about whether this means that the bezel needs to be an internal bezel (like the one on some of the IWC aquatimers).  With an internal bezel, you just turn a crown to turn the bezel, but the bezel is under the crystal, and is therefore protected from sand and salt.  However, it does change the look of the watch a lot - I'm not sure if a "perfect" dive watch should have an internal bezel...

Finally, I'm a bit torn on whether the bezel should be one colour or two - in a lot of traditional dive watches, the first 15 minutes of the bezel are a different colour.  Not sure why that is - I would understand it if we were counting down (last 15 minutes you can be underwater) but on almost all of these bezels, we're counting up.  I'll have to look into the significance - now it's really staring to bother me.

4.  Tough, reliable watch

The ISO certification has requirements for magnetic resistance, shock resistance, chemical resistance, strap/band solidity.  It also nees an End of Life indicator on a battery powered watch, and an indicator that the watch is running.  Makes sense to me.  You don't want the watch falling off in the middle of the ocean.  You want to know that you're not going to run out of batteries in the middle of a dive.  You want to be able to glance at the watch and confirm that it's still running, and doing what it needs to do.  Theoretically, you are depending on the watch for your health and safety.

Also makes sense that the watch should be able to withstand the corrosive nature of seawater.

5.  Looks like a Dive watch

I think it's important for a dive watch to look the part.  It should have a metal, rubber, or fabric strap.  A big, easy to read, black face.  A serious piece of metal on your wrist.  It should be devoid of fancy features that decrease legibility - no chrono dials, preferably no date indicator (though, if you must, one with a black background).  Although the quintissential dive watch (the Rolex Sub) has a cyclops magnifier for the date window, I would do without - it distorts the face, and sticks up too much (it will get banged up and scratched).  This is a utilitarian watch.  Oh - and I think it should have a wetsuit extension clasp if it's a metal band, or an extra-long bracelet if it's rubber or fabric.  It should have a safety clasp.  Big thick hands.  And a screw-down crown.  I'm not too fussed about fancy shmancy "helium release valves", depth guages, trip computers, or any of those things.

So this wednesday, we'll take a look at our first dive watch.  And we'll look at another every Wednesday 'till I get bored and decide to look at other types of watch for a change.