I'm a sad nerd about stuff like this. I think that's a Omega121-002-62 (had to look that up, mind) and - at a guess - early 1960s. The movement should be a cal. 269 - they're lovely things from when Omega were making properly good watches.
If you want to see what it looks like, here's Christian Dannemann taking one apart (and putting it back together again):
https://watchguy.co.uk/service-omega-calibre-269/
It'd clean up beautifully - looks like most of the marks are just on the plexi crystal and would polish out. Definitely worth getting it serviced. Value? £500 on the low side, £850ish high side.