Looks like a 25945200. Please note that this watch has a Cal. 3301 or 3303 inside, which is an F. Piguet based vertical clutch chronograph movement, and parts will potentially be a problem for someone who doesn't have an Omega parts account. There aren't parts floating around on the open market for this movement like there would be for a 7750 based watch, so this is a bit more specialized.
Depending on when this watch was made, the movement may be subject to required upgrades that make the chronograph system more reliable, so parts may be required for that as well. If the owner actually gets this watch wet, you will want to have all the seals replaced, and there are individual seals available from Omega for the HEV, and the pushers (that's 6 seals in those three items), as well as a case back seal. The crown doesn't have a seal available for it, so a new crown would be the way to renew that seal.
All this can add up quickly, and since according to my instructor at Omega, not many of the watchmakers they train go on to service these (many just send it in to Omega) you might have trouble finding someone who is familiar with the movement. I personally like working on them, but not everyone does, so if you choose to go with an independent, make sure they can get the parts and have experience with this movement.
Or just send it to Omega and be done with it.
Cheers, Al
