deville gmt - what movement is in it?

Okay - bear with me here....I will try to keep this simple, and I won't go over all the differences between these movements because there are a few (beat rate, design of the pallet bridge, etc., etc.). The one design difference I mention below is the really relevant one in my view.

The Cal. 2500 came in 4 versions, so A, B, C, and D. The first 3 versions (A, B, and C) all have potential problems related to being 2 level co-axial escapements. The D version is a 3 level co-axial escapement, so it does not have the potential for the specific problem that the other versions do.

Based on the serial number of the watch you are looking at, the watch has a 2628B. The 2628 comes in 3 versions, so the A, B, and D.

If you aren't confused enough, here is how the versions shake out:

2500A - not used for the 2628
2500B = 2628A
2500C = 2628B
2500D = 2628D

So with your watch having a 2628B, the movement is based on the 2500C with the GMT added.

My preference for any co-axial would be a 3-level design, so the D version of the 2500 or 2628, but of the other versions, the C is the next most reliable in my view.

Hope this helps.

Cheers, Al

The movement may stop or may not. Omega offers a solution for it at service, and to date that solution has been working okay. If you search on 2-level co-axial escapement I'm pretty sure I have explained this issue in great detail previously.

Based on the serial number, the watch should be a 48334031. 1671702 is a partial case reference, and the seller likely opened the back and saw this number inside the case back, so they think it's the reference number.

Cheers, Al

Those only came with the 2500D.