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The OMEGA Seamaster 300m Apnea
Ref: 2895.30.91, introduced 2003
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OMEGA Technical Information

Details on shock, water, and temperature resistance, special markings, and glow-in-the-dark technologies

  1. I don't have my instructions handy. How do I wind and set my OMEGA?
  2. What temperature extremes can my OMEGA watch handle?
  3. How water resistant are OMEGA watches?
  4. Why aren't the Speedmaster Moonwatch and X-33 Mars Watch more water resistant than 30 meters?
  5. How shock resistant are OMEGA watches?
  6. What grade of steel is used in modern OMEGA watches?
  7. Which technology is used to make the dial and hands glow in the dark?
  8. Why has the 'true' Speedmaster Moonwatch not been upgraded to a sapphire crystal?
  9. My OMEGA does/doesn't have a star stamped on it? What does that mean?
  10. What is the meaning/purpose of a red dot on the back of the case?
  11. How can I tell I am getting the current model year OMEGA watch?

I don't have my instructions handy. How do I wind and set my OMEGA?

Here's a quickie instruction set covering most typical OMEGA watches. Models with digital displays or special features may operate differently from what is described here.

This set of instructions is probably more comprehensive that what you will see in the original owner's manual anyway. Watch instruction manuals are notorious for giving only terse info, skimpy details, and cryptic diagrams--though at least they do it in 6 to 12 different languages so the entire world will be equally confused.

Some models like the Seamaster Professional have screw-down crowns. To open the crown, simply turn the crown anti-clockwise to unscrew it (takes about 4 or 5 turns). To close it back, push it in while turning clockwise. Do not close it real tight, just with mildly firm finger pressure. Also if you have a helium relief valve, check that it is closed similarly. It is the threading that provides water-tightness, so over tightening does nothing to increase the water protection and can overstress the metal. Once the crown is unscrewed and in the "neutral" position, it operates like any normal watch.

On a mechanical or automatic watch, when the crown is in the "neutral" position, turning it clockwise (if viewed looking at the logo on the crown) will wind the watch. 20-30 turns should wind it fully. Turning it backwards does not hurt anything, but it accomplishes nothing either. It is perfectly okay to manually wind any mechanical watch--even automatics.

On a quartz watch, turning the crown while it is in the "neutral" position does nothing.

On most modern watches that display the date have a "quick-set" feature where pulling the crown out one click and then turning the it allows you to roll the date forward. Others only change the date by rolling the hands forward 24 hours for each day. Older OMEGA watches sometimes used more unusual methods of changing the date. In particular, watches based on the OMEGA 600 series movements from the 1960's advance the date once when you pull the crown all the way out. Rolling the date forward multiple times on these watches involves pumping the crown out and in repeatedly!

It is generally NOT a good idea to change the date on a non-digital watch within +/-3 hours of midnight. Remember, the watch date mechanism is mechanical (even on a quartz watch), so uses gears and other components to advance the date. Manually changing the date while the mechanism is engaging can push the gears out of alignment. Normally, this does not cause damage, but can alter the exact time that the date will change--usually further from midnight.

Some modern OMEGA quartz models have a "timezone" feature that allows changing the hour hand without altering the minutes or seconds. On these models, pulling the crown out to a second click and then turning it will move the hour hand forward or back entirely independent of the other hands. This feature is great for frequent travelers.

Pulling the crown all the way out allows you to set the time. It is usually best to turn the time forward. Backwards is okay on most modern watches, but it is usually not a good idea to turn the hands back across midnight, else you might confuse the date change mechanism.

On many watches, when you pull the crown all the way out to set the time, this enables the "hack" feature that stops the second hand. Stopping the second hand allows you to restart the watch by pushing the crown back in to synchronize the watch to an accurate time signal or other clock. For an accurate time reference, try The Official U.S. Time Clock.

And finally, if your watch has a screw-down crown, don't forget to close it back after you are finished setting or winding the watch.

More information on winding and setting watches--especially on common confusions with setting the date correctly---see the Chronocentric section Owner's Guide to Fine Wristwatches.

What temperature extremes can my OMEGA watch handle?

OMEGA reports that the mechanical movements used in their watches use oils that allow the watch to operate at temperatures between -20 and +70 C (-2 to +158 F). Remember that the inside of the watch must reach that temperature. That is not terribly likely when you are wearing the watch on your arm--even while diving in very cold waters. If your body ever reaches -20C (-2F), then your watch is unlikely to be your topmost concern at that moment.

Your mechanical watch should continue to run at up to these temperatures. But near these extremes, the mechanical accuracy may vary more than normal. Yet a quartz watch is not always better for use in extreme temperatures--the electronic circuits used in a quartz movement will stop operating at cold temperatures that do not stop a mechanical watch movement.

Of greater concern are how sudden extreme changes in temperature can effect the water resistance seals of the watch. For more information on this, read the major section on Water Resistance.

How water resistant are OMEGA watches?

All current OMEGA watches come from the factory with at least a 30m/100ft depth rating water resistance--sufficient to handle basic water activities like hand washing, swimming, and other light water activities. This includes the Constellation, Speedmaster and DeVille models. The Dynamic comes with a 50m/150ft depth rating. And for the best depth ratings, the Seamaster line has models rated for 120m/400ft, 200m/660ft, and the Professional series which is rated for 300m/1000ft.

It is very important to understand that water resistance is not permanent. Your watch's ability to resist water entering it depends on rubber seals that must be checked and replaced regularly to ensure that age, temperature, and other conditions have not weakened them.

For a more detailed discussion of water resistance, including much more information on interpreting the rated depth measurements, read the major section on Water Resistance.

Why aren't the Speedmaster Moonwatch and X-33 Mars watch more water resistant than 30 meters?

The Speedmaster Moonwatch and X-33 are only water resistant to about 30 meters. This leads many owners to ask why OMEGA chose to not give them greater water resistance. But additional water resistance is not always an advantage.

Highly water resistant watches are designed to handle environments where the air or water pressure outside the watch is greater than the pressure inside the watch. A diving watch like the Seamaster Professional series that is rated to 330 meters can handle an external pressure of up to 30 times the watch's internal air pressure. The Speedmaster Moonwatch and X-33 are rated for 30 meters, or only about 3 times their internal pressure.

But pressure works both ways. Yet none of the normal water-resistance features allow a watch to handle excessive internal air pressure, which can occur using most any form of pressurized environment--a deep diving chamber, a spacecraft or even in a commercial jetliner.

  • In a deep diving chamber using a helium rich air mixture, helium--the smallest molecule--seeps past the seals, allowing the watch's internal pressure to gradually equalize to the chamber's pressure. During decompression of the chamber, the helium cannot seep out fast enough, causing the pressure in the watch to exceed that outside of it.
  • A watch on the outside of the astronaut's spacesuit will be exposed to little or no air pressure when he steps out for a spacewalk or on the surface of the moon.
  • In a commercial jetliner, you are in a pressurized cabin because the air pressure at high altitudes is very low. On rare occasions, the cabin pressure may drop suddenly, causing the pressure inside the watch to be greater than outside of it.

The end result is that due to any these several reasons, the air pressure inside the watch becomes greater than the air pressure outside the watch. The tigher seals of a highly water resistant watch can prevent these pressures from equalizing as quickly as they might change in the environment. The weakest seal for handling internal pressure is that holding the watch's crystal. When internal pressure exceeds that seal's limits, the pressure will escape by causing the crystal to pop out.

This is why the Speedmaster Moonwatch and X-33 are not made waterproof to great depths. These air pressure difference issues occur in routine space mission events, rendering a watch that cannot handle them a danger to the mission.

How shock resistant are OMEGA watches?

OMEGA reports that the full size Seamaster Professional Diver Quartz is shock resistant to 5,000 Gs. The OMEGA X-33 "Mars watch" is shock resistant to 3,500 Gs. The lower rating on the X-33 is due to the digital display, which NASA requested despite it being relatively more fragile than a traditional watch display.

OMEGA does not report specific shock resistance values for their mechanical watches. But they do confirm that all their watches--mechanical and quartz--are tested against shocks according to the Swiss standards of the industry technical specifications NHIS 91-10 and ISO 1413.

What grade of steel is used in modern OMEGA watches?

OMEGA uses stainless steel 1.4435 or 316L. Rolex uses stainless steel 1.4439 or 904L which is slightly different from 1.4435. Steel 904L and 316L have the same grade of hardness.

The grade of nickel discharge with 904L is slightly higher, causing an increased chance of allergic reaction when worn by people sensitive to nickel.

While technically, 904L has a slightly higher resistance to corrosion, this is only noticable under extreme conditions that a wristwatch should never face. Where this is mainly of concern is in industrial applications using steel in equipment for handling chlorides, sulfur dioxide gas or other toxic materials.

The differences for use in wristwatches is quite nominal. Almost no watch manufacturers except Rolex consider it worth using the 904L steel, especially given that the price for 904L is approximately three times that of 316L.

Which technology is used to make the dial and hands glow in the dark?

For many years, OMEGA used phosphorescent material excited by tritium. It is a common misconception that the tritium is what glows. In truth, the phosphorescent paint produces the glow--tritium is a mildly radioactive material that is added to the paint to continually excite the phosphors in the paint, causing it to glow all the time. The nominal amount of radioactivity in the tritium is not a safety hazard. It is so weak that even the crystal of the watch is more than sufficient to block it. As with all radioactive materials, tritium loses its effect over time, so dials with tritium will lose their additional glow over time.

For ecological reasons related to the manufacture and handling of tritium, OMEGA ceased all use of it at the end of 1997. They changed to a non-radioactive technology called 'Super-luminova'--the first replacement for tritium that was really effective. A couple of hours exposure to light is sufficient to keep the Super-luminova glowing all night. OMEGA says this technology will not diminish its effectiveness over time like tritium does.

Tritium enhanced dials should have the letter 'T' on both sides of the 'Swiss Made' at the bottom of the dial. Super-luminova dials should simply say 'Swiss Made.' This is not a precise indicator since OMEGA did not perfectly synchronize the change in dial printing with the change in phosphor technology. To be certain, you can contact OMEGA with your serial number and they can confirm the date of manufacture and which glow technology was used.

Why has the 'true' Speedmaster Moonwatch not been upgraded to a sapphire crystal?

Back in the 1960's, many watches used either mineral glass or acrylic (plastic) crystals. These are not difficult to scratch, but very inexpensive to replace. Now though, most all luxury watches use the highly scratch resistant synthetic sapphire crystals. Yet while OMEGA offers the sapphire crystal on all their other models, the classic Speedmaster Professional "Moonwatch" still uses the same Hesalite (a name brand of fine acrylic) crystal as is did decades ago.

The reason for this is directly related to its certification for use in space. While sapphire crystals are less prone to scratching, they can be shattered. When shattered, they break into tiny fragments that would be hazardous in a zero gravity environment.

So the Hesalite crystal is maintained on that specific model as a safety feature for its use in space flight missions.

OMEGA has since added a similar model SpeedMaster Professional that does have the sapphire crystal, but the original version with the Hesalite is stil the 'true' Moonwatch.

Many people ask about upgrading the Hesalite crystal on their Speedmaster Professional "Moonwatch" to the sapphire crystal found on the similar Speedmaster Automatic. But this is not possible. While the watches appear very similar externally, the shape and fittings of their crystals are quite different and are not interchangable.

My OMEGA does/doesn't have a star stamped on it? What does that mean?

OMEGA sometimes uses a small star stamped on the back of the watch during part of a production run for internal production monitoring purposes. Such indications are internal to OMEGA and have no discernable meaning or significance to the end user. Do not waste your time thinking this is important or that a watch with or without the mark is in any way superior or inferior to one marked differently.

As with any company producing products on an assembly line, OMEGA will occasionally use a different part, technique, or equipment at various stages of the manufacturing of their products. The star is sometimes used for a brief period to flag the ones that they want to track separately during the quality testing phase to monitor improvements in product quality or manufacturing efficiency brought on by the new or different component/process/supplier/material.

The presence OR ABSENCE of the mark on any particular watch is no cause for concern to you. It is neither a sign of superiority or inferiority. No matter which assembly line, production run, component batch, or anything else went into the production of your watch, they all passed the OMEGA quality control phase or they wouldn't have left the factory.

What is the meaning/purpose of a red dot on the back of the case?

On many models--especially the one with screw on backs, OMEGA puts a factory seal put on the back. It is a small paint-like mark across where the watch back meets the case. Opening the back of the watch destroys that little red spot. This allows you to see that the watch has not been opened since it left the factory. So it ensures you that the watch you have bought is "factory fresh" and has not been repaired or altered by an unauthorized entity.

Typical location of red dot seal on back of a Seamaster Professional [Derek Ziglar]

Once you get the watch and see the spot is intact, it is no longer important. It will likely eventually wash or wear off and there is no cause for concern if it does.

How can I tell I am getting the current model year OMEGA watch?

Watches are not like cars where the entire line gets updated to a 'new model year' every 12 months. Watch manufacturers seldom change existing models from year to year, so you will not normally have a 1999 versus 2000 model of the same watch. When you hear about a 'year 2000 model' what that really means is that it is a model *introduced* during the year 2000.

All the models that existed before the current year are normally unchanged and do not have any differentiation--so the 'model year' concept is meaningless. Any changes of significance usually are designated by a new model number on the watch. In a few rare cases, OMEGA might improve a model internally without changing the model number, such as around 1997 when they upgraded several automatic Seamaster, DeVille and Connie models from the 1109 to the 1120 watch movement. But these still do not have a 'model year' designation--the change was indicated by the movement number designation on the 'hang tag' that came on the watch.

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