This appears to be a 1940 Ambassador on original band with movement double stamped as 1939 and 1940 (Omega and Shield).
Hands would appear to be replacements, and watch has many jeweler's marks inside of caseback. I'm intrigued by the face, which has a unconventional center detail line and sub-seconds track. All detail is raised gold, but face lacks "Bulova". White surface of face is chalky, like it was poorly cleaned so it's unclear if this is a Bulova face with ID cleaned off or an extremely good quality replacement. Face also shows old "halo's" around hand shafts apparently from an excess of oil during a service and soiling around perimeter matching crystal opening - this appears old. I mic'ed the dimensions of the outer seconds track, face and case and it's identical in size, shape and dimensions to my 1939 Ambassador "B".
No other use of this face found in the Db, so it appears to me that this isn't a swap from another watch. Thoughts?