You've no doubt seen this
http://www.littlegun.be/arme%20belge...14367%20gb.htm
The proof marks indicate that at least the barrels, and likely the action was made in Belgium, and possibly finished in Galand's shop in Paris. Very common.
When you get a chance chalk the intertwined antlers marks and I'll try to ID the maker.
18.4 = .724" which would be the standard 12g bore of the time.
Apparently there were some 3 1/2" and 4" English 10g black powder loads in the 1880s. In the 1890s Winchester offered the 10 gauge in 2 1/2, 2 9/16, 2 3/4, 2 7/8, 3, 3 1/4 and 3 1/2 inch shells.
The Belgian Proof House typically marked the bore at the time of preliminary proof, and it is possible Galand bored the barrel and chamber to 10g in Paris.
Have you measured the end-of-chamber wall thickness?
Odd that it is marked CHOKE.
NON POUR BALLE was used for choked unrifled bores 1878 - 1897
Hybrid Mode