Model 10-8 Heavy barrel 5D95xxx
SN's ran from 4D00001 to 6D10000 that year.
It could be one of three possibles:
A .32 Hand Ejector or Regulation Police, both built on the small "I" frame with
serial numbers running from 536000 in 1946 to 721953 in 1960.
Or, far less likely, a K-32 1st Model. They are very rare and built on the "K" frame.
Either way, they were all chambered for the .32 S&W Long cartridge and will also fire the standard .32 S&W (short).