[DonVoigt]

Dwight,
one more point:
"If this was, indeed, a post-war assembly intended for a U.S. GI, it would assuredly not have any sort of German proofs as there was no government to proof them."

Why?
There was just as much "government" to cause the proofs to be applied to the pistol we see in the OP, whether for the domestic market or other sales. Black or grey market sales to GIs would have been "domestic" sales for all intents and purposes.

Perhaps use of proof and the proof stamp was so ingrained in the industry, that even in relative anarchy, assembled pistols continued to be proofed, and received the stamp- whether or not it was mandated by any government or authority(occupation) at the time?