If you're able to post some pictures with better lighting it would help immensely. But regarding the differences you see on Omega's vintage database... don't take too much stock in what it says. While it's a great resource, my watch below points to a completely different watch than what is listed in their vintage section: https://www.omegawatches.com/en-us/watch-omega-other-omega-ck-2451 There was a lot of variation with these watches back in the day, and Omega's own records can be murky. I know for a fact that my piece is all original, it has been verified in person with a highly knowledgeable collector, but even Omega themselves aren't able to send me an Extract because of a fire at their old headquarters which resulted in a loss of records. Sometimes your best bet is to search the reference on Google to see if there are other confirmed examples matching your watch to the information on the case back.
- What is the difference between a 2515-2 and a 2515-3? The latter was produced later – that's it. - What is the difference between a 2515 with a 333 caliber, and a 2515 with a 332 caliber? The base caliber is the same, but the 333 was tuned to chronometer standard (higher accuracy) and featured some better and/or different parts. The most obvious difference is that the 333 had a "fine" regulator, while the 332 had a standard one. - How much is this watch worth? These large bumpers are nice, but the dial has more "patina" than most collectors want. Also, the gold bezel os not to everyone's taste. Probably a rough value range of around $500-600.
I think that Seamasters normally (or maybe always) have screw-on case-backs, and most (but not all) are marked Seamaster on the dial. So it's not a Seamaster, but I don't think it matters if you like the watch, and I assume you like the dial patina and the two-tone style since you purchased it.
Old thread I know, but ran across this for sale at Omega Enthusiast that sheds some light on yours; basically the same watch in a pre-Constellation format? The sales write-up is very interesting. https://www.omegaenthusiastltd.com/product-page/1950-omega-chronometre-automatic-1