Hi so I have the below watch. I got this passed down from my FIL. He was originally gifted this by his friend. The strap seems to be worn off a bit and I can't seem to locate the serial number.. Any details of this watch please..

 

As with most (all) Omegas the serial number will be on the movement.

 

That back will snap off, it’s pretty easy to remove with a (dull) blade between the silver and gold part.

A reference or model number may also be on the inside caseback as well.

 

https://omegaforums.net/threads/how-do-i-identify-my-vintage-omega-watch.93146/