Friend of a friend brought me a very rusty (but shootable) S&W Military & Police 4 screw pencil barrel 4" .38 Special. Serial number was C173XXX. Obviously pre-Model 10. I cleaned off as much rust as I could and will return it. I think the serial number indicates manufacture in about 1951. Any opinions? I intend to recommend a refinish by a competent pistolsmith as it still shootable. I wonder how they keep the rust out of the cylinders and barrel while the guts and exterior are allowed to degenerate.