I just picked up the same on off of CL about 3 weeks ago. The drive plug on mine was made by P&C a Plomb owned company starting in 1941. Mine has the wrong screws holding it together, but I have the correct ones to restore it. The former owner used straight slotted screws. He did use ones with the correct thread pitch, so no side cover damage. I also have the 1/2 inch one. Now I need to get the 1/4 inch one.
EvilDr235