thanks gatorcpa, I knew it was from 1910 onwards, I did not know that the case was not made from omega, I think this case is bronze, others as you say.
If that's just under 30mm, it could be a 13-ligne movement, which is a 0 size case, and you might be able to swap cases. Looks like it's not negative set, so any case without a crown might work. You'd have to consult your watchmaker.