Wow, great responses and info.
Just guessing, but I would think that the mail employees on those cars would have been issued the standard, plain vanilla, incredibly common, S&W Model 10 M&P (military and police), in .38 long colt or .38 Special, sold in many variations from 1899 up through the 1960s, with over 6 million of them made. This was the standard issue for hundreds of police departments and federal workers across the country into the 1960s. A very poor weapon indeed, since it fired a plain lead 158 slug at medium speeds, which had little penetration or stopping power. It was often called the "widow maker," not because is stopped bad guys, but because it often ended up with the policeman getting killed by the opponent, who had a better handgun, such as a .45. (The .45 of course had great stopping power, but its recoil made it difficult to master for multiple shots, and police departments and most federal agencies spent little or nothing on regular target practice or firearms training for their personnel.)
Barney Fife carried one.
Thanks,
Mannyrock
