These were cosmetic machined G.43 receivers made by M.A.S. in St. Etienne, France. If I remember correctly the theory was they might have been shipped from Buchanwald to one of the two Walther plants at the very end of the war and assembled. They're not super common, but not super rare. You sometimes see dual marked K.43 and G.43 in AC45 receivers, too. Those are pretty scarce.
Hey! I'm somewhat new to this, but from my understanding, rifles made after '44 are marked K43 in lieu of G43. Any explanation as to how this rifle ended up with a G43 marking? Thanks!