The gun is Belgian and of very high quality. It was made by Auguste Francotte (AF), a top maker of the time. See http://littlegun.be/arme%20belge/art...cotte%20gb.htm
for more information.
The rib marking may be English or American, and is the retailer who first sold the gun. I can't find anything on that name/company, though.
While I have no doubt that those Damascus barrels were the best made at the time, I strongly recommend not firing any Damascus barrel shotgun with any ammunition, even black powder. I know others will disagree, but if the barrels have weakened over they years they might blow and it would be a shame to destroy a beautiful old gun.