Help identifying antique Omega

I was recently gifted this watch by my grandfather who told me it was quite a vintage (1920/30’s) Omega.

I’ve been trying to identify it and while the face and case looks quite similar to some I have seen the crown looks quite a bit larger, as well as the part that holds the strap to the case looks like a recent addition.

I don’t have an internal photo, however it was recently serviced and the fella said it was likely from the 20’s / 30’s.

Any ideas would be great thanks!