Looks like a very nice Omega 2576 from the 1950s with a bumper movement, either a caliber 342 or 344. Taking off the caseback will let you get the reference number, the caliber number and the serial to date it more exact.
It looks like a nice original piece, and all it will need is a movement service and crystal polish!
If you use a wrench incorrectly, it could mess up the notches. You could try one of these case remover balls for a few bucks.
If those are scratches, personally I would try to polish them out...they look pretty deep though. If they're cracks you have no choice but to replace it unless you want to keep it as-is!
If they’re real deep, wet and dry paper may be required first.
Looks really, really nice under that crystal 👍
I’ve started using sandpaper first just about every time I polish a crystal now.. it all goes much faster that way. But if you do, make sure you fully tape off the case to prevent scratches.
