Berdan Primed 45 auto?
While cleaning old 45 brass of unknown origin I found what appears to be a Berdan primed piece. I manually deprime before cleaning so there was no damage to the depriming pin in the press. Around the base are the letters and numbers as follows: 57,I,1,SF. Not an expert on 45 ammo by any means but this seems kind of odd. Can anyone tell me what it is?