Joe
When the military arms depots rebuilt them they would often replace eroded/worn barrels, stocks, sights, any other parts that required replacment or updating and reparked (they were than put into storage as "ready to issue"). In the early 60's a high percentage of them were rebuilt just this way (Korea put a lot of wear on a lot of rifles) and several arms depots were fully involved in the work.

Mine is a Rock River (RRAD stamped) rebuild, with a IIRC 1963 (might be 64) dated barrel and a contractor made Beech stock (Obermeyer?)

SA purchased a number of these rebuilds, when they were surplused. IOW all they did was take a hacksaw to a otherwise "like new" rifle. They simply added their "stamp" after they finished hacking.