On the bottom of my Parker VHE 16 gauge barrel flats there are some # stamped they are PG3AG and on top of those letters are RH stamped,any idea what these # are? thanks(this is a Remington Parker)

Sounds like Remington date and repair codes. P would be June and G 1938. R would be November and H 1939. I don't know of anyone identifying what repair would be signified by the 3 or the AG after it.