vintage omega watch

Welcome to OF. This looks like a nice watch gold Omega Constellation probably 168.029 from around 1970. Movement is probably 751. Looks like 14k gold and bracelet. Worth quite a lot in gold value alone but the watch itself if desirable too.
Take it to a watchmaker and have them open it and take movement photos and photos of inside Caseback this will confirm reference and movement. Also ask them to get serial number photo ( on movement).
Your best bet is probably eBay if you have someone
who can help organize this. This looks like good original example and should bring around $2000 I would say. You can’t sell it here as OF rules require considerable presence and participation before being granted sales privileges.
Good luck hope this helps.