Sir- I cannot say with certainty- need close up pics of the barrel markings with LOTS of pixels- but that APPEARS to be a Belgian made shotgun with Damascus barrels.
Take a close look at the stampings. I think one of them may look like this:
That is the mark of the Belgian proofhouse at Liege, Belgium.
Do not know if you are familiar with Damascus style barrels- they were made by taking strips of iron and steel, wrapping them around a metal rod, heating them and hammer forging them until they fused- and then the rod was driven out. This style was fine for the pressure of black powder- and when the barrels were new. Not fine for smokeless powder. Each of the thousands of welds is subject to corrosion from black powder, and, if sufficiently weakened, COULD fail in a violent manner upon firing. And that gun likely has 125 years or more of aging.
I would not fire any
original muzzle loading Damascus gun with anything- but that is because I really like my fingers where they are.
Nice shotgun- deserves a retirement to a place of honor- above the fireplace. PS- If you have not done so, please be sure to use a ramrod, and check that there is not a load sitting in the barrel. Found one late last year, still loaded.