Looking for some Omega chronograph movement help

Hi everyone. This week my impulses got the best of me and I picked up this vintage solid gold Omega chrono without doing my due diligence. So... (A) forgive me father for I have sinned, and (B) Can anyone please help me in identifying this movement, that may or may not be an unsigned Cal 321? I'm told the bridge was replaced, hence no omega signature, but when I hear that I become instantly skeptical about the movement as a whole. On the bright side it was a lowball offer that got me into this mess and if it's not the original movement I have grounds to return it.

Thanks in advance OF friends.

Okay thanks so much for that info. It is pretty early (probably early 50's so that makes some sense. Looking at other movements online it does look pretty rough, and the crown doesn't feel original either. Something to think about...