Help to ID calibre No and ref Omega bumper

I have just bought this lovely bumper dated back to the forties, an American cased probably...
I would want to identify the watch calibre (OXG marking) and reference if possible.
Please help me with info on this.

Thank you for insights and nice weekend.

Hi @Dan S
Following your suggestion I measured inner case, it is 30mm.

Hello
Under balance wheel I can read "28.10 RA". So the caliber is from 340s family as per Ranfft's data base.
Was not skilled enough in photography so no pic attached here. Sorry.
Regarding dial I think this is an "enhanced dial" with the previous owner had had probably made done.
I meant lacquer is still there, but some parts of it are gone. Numeral prints in yellow tone with some pearly tone on yellow.
What I am sure is that the watch maker enhanced dial look with black paint surrounding numerals to make number look more neat.



Sorry for my description in poor English.
So I think it is - at best - a retouched dial, at worse a very old redialed.
Otherwise case is gold plated in thickness as you can see on pic below.


What are your thoughts please. Thank you in adavance OF members.

To my eyes it looks like the print is correct, but at some point the dial was cleaned, leaving it stark metallic in appearance as the yellowed laqcuer was removed.

Dial in dull daylight. Please share your thoughts.
Thank you.

I agree about the cleaning of the dial. From my experience, when the lettering thickness varies in this way it’s from having the dial cleaned. It would have been best left as it was regardless of how yellow or discoloured it had become.