Some years ago, whilst researching “The M1911 Complete Owner’s Guide,” I came across a Pachmayr custom M1911 in .22 Long Rifle. It was built with a .22/.45 Conversion Unit. Nothing particularly puzzling there, except for one nagging question: what was the source of the frame? Clearly, the frame was produced prior to 1968*, at a time when, while the serial number (if present) of American-manufactured firearms was to be marked on the frame or receiver, the manufacturer was free to place the company name and address and model name anywhere it chose. In the case of automatic pistols, generally, the manufacturer and model were marked on the slide, with the…