The following is a little speculation on my part.
The forend looks a lot like the forend on my current French 16ga sxs, a prewar St. Etienne gun, right down to the checkering pattern. The rest of the layout looks a bit like some Belgian guns I've seen.

What about the gun having been furnished in the white by a Belgian firm to someone in Italy, who then finished it and had it proofed in Italy?

fiery, dependable, occasionally transcendent