Doug-

Thanks much for looking. Perhaps the B stamps are an indication of Belgian manufacture? The similarity of the proof mark to both German and French proofs would perhaps be a characteristic of this border nation?

I have been trying to figure out what the "Q R" might stand for, as this might be a clue.

I wish I knew more about where this gun came from. I picked this gun up in South Texas (Rio Grande Valley) along the Texas Mexican border. For a time Mexico (and Texas) was under the French realm. If the gun has been in this area for a long time, it is possible that it was made in Mexico by a German immigrant (or brought into Texas by an early Texan). It is also quite possible that it was brought down here by a Winter Texan from anywhere in the US.

Doug