I saw that stamp on a trade gun lock. The gun was in great shape and although it was flintlock it had some characteristic of more modern tradeguns. It was bigger bore than the usual .20 or .24 gauge, more like .16 or .12 gauge. It had a flat lock plate, and a double thought cock. The only mark on this gun was like the picture you show, stamped just between the cock and the pan on the lock plate. I always assumed it was either made in Belgium, or France because it didn’t have all the proofs like the British trade guns. But it might have been made anywhere, including America.
Hungry Horse