Drew, the whole "maker, outworker, retailer, finisher, peddlar" thing on the continent is overwhelming.
One of the locks shown in the montenegrin's posts has the two screws just like this one. But no bar in wood.

Ultimately, I bet whomever supplied the locks will be as big a contributor to that shotgun's lineage as is possible to nail down.

When a gun is sold through a retailer, who is "officially" the maker?

Out there doing it best I can.