They did indeed use stainless barrels during manufacture.. Thanks for the pic showing where the stamping lines up..
IF that barrel is a true '48 and untouched, that stamping refers to the .300 H&H cartridge.. It's the proof mark on top that's throwin' me off a little. I checked three of my other pre-64s and the proof stamp is on the LH side, right across from the receiver stamping.
Still, to be absolutely certain, please do a chamber cast..
Last edited by Redneck; 12/23/10.