What have I got here?

[trigger643]

I apologize in advance for knowing almost nothing about Omegas. An associate of mine is presently going through some temporary difficulties as a result of a divorce and has asked if I would be interested in purchasing this (along with other items that I do know something of).

It appears to be a 3513 (?). He stated he'd received it as a gift 15-20 years ago and wore it regularly until a few years ago. It appears to keep time, but probably needs a service.

Your expert knowledge is greatly appreciated.