I'm going to speculate (I have very little French) that the "Eprouve ... Pyroxilees" language means that the gun was proved for all nitro powders. But the other proof marks will tell the tale for sure on that point.
The 165 and 166 would indicate the bore diameters at the chokes on their respective barrels, 16.9 to 17.1 mm (depending on the maker) being a straight 16 ga. I'd have to look at a conversion table to tell the chokes, and that doesn't account for the possibility that in the decades since it was made someone altered the chokes, but my initial guesstimate would be the 165 as an improved modified and the 166 a modified.
Last edited by Dave in Maine; 10/31/11 12:27 PM.
