Ken - I'll try to help you. My Marlin era gun only has the serial number and "Field" stamped on the receiver watertable, so no issues there. The Pacmeyer pad is a replacement. Based on the serial number it appears to be late production Marlin gun and I understand some of the shotguns near the end of production had no markings on the barrels...so is it possible that some late guns did not have the L.C. Smith roll-stamped on the locks? I don't know.
I'm not sure what the upside would be to swap one set of locks with another (or how easy that would be)? Also, it sounds like the fit and finish of the locks match the gun. As Dan said, if you can look at the serial numbers on the inside locks you will know for sure.
Maybe someone else knows about or has seen this before?