It looks like one of the RB shotguns made in Belgium in the 1900 time frame, or it may be a shotgun made from one of the many rolling block military rifles used in Europe at one time. Take the foreend off and see if there are proof marks on the bottom of the barrel. If it is Belgian, one may be an oval with the letters "E L G". If anything else, see if you can describe them. I think it is a fairly safe bet it is not Remington.
It is good that you intend the gun as a wall hanger, as I would definitely NOT recommend firing it. It might be a good idea to remove the firing pin and weld up the firing pin hole so it can't be fired.
Jim