Symetrical clutch bridge indicates an early movement so is it anything to do with the SN having only 7 numbers?
You are welcome and I thank you for your contribution. Just compare some pictures of Omega 27 chro in the range 9 millions with the one shown at the beginning of this thread.
I still don't know the answer, but I do believe that the movement is not all original as I tried to imply in my first response (although now I realize I was not clear at all in that post). My assumption is that an 9M Omega serial would be from the early 1940s, and that an Omega chrono movement from that era would not look like this. Presumably it wouldn't even be shock-protected.