Omega Caliber 2500 Complete Guide
In recent years, Omega has focused more and more on developing and manufacturing its very own in-house calibers. Earlier, Omega used a lot of off-the-shelf movements from manufacturers such as ETA, and then modified them according to needs and requirements.
In developing your own in-house calibers, you also need to come up with technology solutions that give the movement characteristics that you would want. In terms of movements, this often relates to anti-magnetism, power reserve, durability, and resistance to shocks, to mention a few.
So what if you combine an off-the-shelf ETA movement with your own developed technology? Then you have the Omega caliber 2500.
In this post, we will go into detail about the Omega Caliber 2500.
Omega caliber 2500
The Omega caliber 2500 is, at its core, an ETA movement, modified by ETA. It is originally born as the ETA 2892, and then modified to become the Omega Caliber 2500. So with that said, unlike what the name might suggest, it is not an in-house movement. But then again, what exactly is a truly in-house movement? Swatch Group, after all, owns both Omega and ETA.
The major change with the movement is that it is equipped with Omega’s Co-Axial escapement. The reason why this movement is so notable and historically important is that it is the first movement commercialized with the Co-Axial escapement. The Caliber 2500 was originally introduced to operate with a frequency of 28800 but was then changed to operate at the rather unusual 25,200 vibrations/hour, which Omega determined to be optimal. The rate was changed from generation C onwards. Reducing the frequency means less wear on parts and thus longer service intervals.
The Caliber is an automatic mechanical movement and was introduced in 1999. The movement has a free-sprung balance and operates within COSC of -4 to +6 seconds per day. The movement has a power reserve of 48 hours. It has a diameter of 25.6mm and displays hours, minutes, seconds, and date.
Omega Caliber 2500 Co-Axial escapement
Omega invested heavily in the development of the Co-Axial escapement, so the release of the new escapement technology is a huge technical feat for the brand.
The Co-axial escapement was invented by George Daniels and patented by him in 1974. He then sold the technology to Omega.
”The Co-Axial escapement functions with a system of three pallets that separate the locking function from the impulse, with the pushing, as opposed to the sliding friction of the lever escapement, resulting in greater mechanical efficiency. The critical virtue of this escapement is the virtual elimination of all sliding friction, theoretically resulting in greater accuracy over time and longer service intervals.”
Omega Caliber 2500 generations
The movement comes in versions 2500A, 2500B, 2500C, and 2500D. It is relatively easy to see which version a watch has by looking at the font of the date.
Omega Caliber 2500A
This was the first generation 2500 caliber from Omega, and also the movement that was in production for the shortest period of time. The reason for this is that it had some issues with reliability. A common issue with the movement was that the Co-Axial escapement can cause damage to the escapement if subject to shocks as it does not have any shock protection, resulting in the watch stopping. When the movement was released, the technology was not proven, which resulted in the production of this version not reaching any large production numbers
Omega Caliber 2500B
The Omega caliber 2500B can be found in the first generation Aqua-Terra which was released in 2003. This movement was refined and improved with new materials for some of its parts. It still showed some tendencies of issues, but to a far less degree than the predecessor.
Omega Caliber 2500C
The Omega Caliber 2650C was released in the Planet Ocean and was yet improved again. This movement is not a movement that struggles with a lot of issues. It is also the movement that got the new, reduced operating rate of 25200 BPH. This movement is the closest in design and structure to the caliber 8500. It got a new escapement wheel on three levels.
Omega Caliber 2500D
The Omega Caliber 2500D is the last, and most modified version of them all.
Omega Caliber 2500 specifications
- Frequency: 28800, later changed to 25200 BPH.
- Jewels: 27
- Power reserve: 48 hours
- Technology: Co-Axial escapement
- Displays: Hours, minutes, seconds, date
When buying an old Seamaster second hand, how can you determine what 2500 movement is inside?
Most sellers just post that it is a 2500, not which variant, which is annoying.
Is there anyway to tell?
Hi,
The only way to tell would be to actually inspect the movement.
Kind regards,
Millenary Watches
The planet oceans are either C or D as noted above. There are numerous small differences but the one I use is the font of the date wheel. In the 2500C the font is the same as the numerals on the dial ie the number 2 has a round smooth curve before it gets down the the cross bar at the bottom like the 2 on the 12 numeral. In the 2500D the date wheel has a different font while the font of the dial remains the same ie the down stroke of the 2 end up with a sharp angle against the bottom cross bar, much like the 2 in the font that I am typing on now
Just a precision: Omega made its own calibers in-house from the XIXth century to 1982, when it was restructured as a plan to combat the quartz crisis. Nevertheless, they continue to produce some of their own movements, some ladies calibers and the 861, later 1861, which was a caliber made in partnership with Lemania, it is a Lemania-Omega caliber. ETA was also restructured in the 1980’s and to be able to produce great quartz calibers, they assembled both Omega’s and Longines’ quartz facilities, laboratories, etc. That is why many quartz calibers were also made in collaboration with Omega or with Longines, and only used by these brands. The automatic calibers Omega used before designing the 2500 were based, indeed, in the ETA 2892A2, but they weren’t “off the shelf”. A caliber 1120, for example, with a 2892A2 base, is so extensively modified, that for extensive parts of the caliber, pieces from a 2892A2 and from a 1120 are not interchangeable. Omega modified the automatic system. Also GMT versions, like the caliber 1128, was a modified 1120, but not any of the 2893/1/2/3. I know it is implied, but I thought it could be useful to precise the point. Thank you for the insightful article.
Hi,
Thank you very much for your comment and the valuable additional details.
Kind regards,
Millenary Watches
Hi, I’m about to buy a seamaster aqua terra 2503.50 and the seller declares that it runs at 28800: I suppose this is for sure a 2500C then, isn’t it? Thanks a lot for the beautiful article, I’ve been looking for a while for this informations.
Sorry, there was a mistake in my previous comment: the sellers declares the movement runs at 25200, that’s why I was asking if it’s for sure a 2500C, according to you. Thanks
If the watch has a see-through case back, the version is marked near the outer edge of the balance wheel (you could ask the vendor to inspect). I noticed this very recently on my 20 year old Omega Seamaster (bought may 2003) using a watchmakers loupe. My watch is marked in capitals ‘2500B’, but once again… the marking is very easily overlooked…
You’re absolutely right – good point! Thatis a great tip!
Kind regards,
Millenary Watches
Very interesting comments from L. Estrada. Thank you.
Is the barrel of the ETA 2892A2 interchangeable with the Omega 2500C?
Thank you for the informative article. I was struggling to find the movement information on my Seamaster Aqua Terra. Could not find it on the web and just this week signed onto the Omega site and asked them for information on my watch (purchased December of 2007). Their reply was “just a 2500”. After looking at your pictures in this article I see where the info was engraved on the watch. I got out my loupe and there it was, 2500C. Thank you!
Very glad to help! Wear your watch in good health!
Kind regards,
Millenary Watches