What's this Omega?

It would help if you opened the case, either by unscrewing it or unclipping it.

For the former, if you haven’t got tools, a squashy rubber ball or dogs' Kong toy, pressed against the caseback can be used. If it’s a clipped-on back, it’s possible to insert a very slim knife blade in the aperture.

You could then photograph the inside of the caseback, photograph the movement, the movement number, and the serial number. And then post the photos on this thread. You need to take sharper and more focussed photos than the one you have posted so a better photo of the face of the watch would also help.

If you don’t feel confident about opening the case, a local watch repairer will generally be happy to do so but may charge you a small fee.

Good luck.