Just to mess around with definitional certainties that turn out not to be that certain at all, please consider this postwar transitional .38 Regulation Police. This is 58470, an early postwar gun. Note the large ejector rod knob and the presence of the strain screw. This is about as "prewar" as you can get in a postwar gun.
Yup, round butt. The frame is unrebated and the stocks are unmodified. The gun letters this way.
Basically, this is a Terrier frame with a four inch barrel on it. I also have 54804 in the same configuration. I think these should have been marketed as the .38/32 Dachshund.
Yeah, I know. I have made that joke before, but I can't stop myself.