Miller,
I have looked up both patents. The 1st is for a monobloc, the 2nd is for a more secure lockup.
Did the method of joining change over time? I am sure it did as in the interim he developed an oven for brazing barrels.
I would not be surprised to find some cheap imitation of a Pieper gun for sale back then. He went to a great trouble filing his patents, in Belgium, Germany and the US. At least those are the countries I am aware of, perhaps there were others. It would have been bad business for him to produce knock off's of his own guns, especially since he often competed for military and government contracts.
Pete
