It's definitely one of the minor brands, but I can't tell you anything about it. If the barrels are Damascus, you'll be able to see a wavy or coilspring-like pattern in the external metal of the barrels because the damascus process was one of hammering wire around a mandrel. But just because it's damascus doesn't mean it won't handle modern nitro loads, and if it's not damascus it doesn't mean it will handle modern nitro loads.
I think your only safe bet is to have the gun nitro proofed to prove its safety. There is an option for re-boring side by side shotguns by machining out part of the barrel and installing the new bores. Both of those options are pretty expensive, with the re-boring costing perhaps $2500 by the time you include shipping to and from England. Nitro proofing might destroy the gun.
Another alternative is to try some light target loads and use a shrapnel absorbing wall and a very long string to pull the trigger, which is something I might try if the gun were of low value, and then work up to more powerful loads. Before doing anything like that, I'd verify the chamber length. It could be something like 2 or 2.5 inches, which is not unheard of, and of course would be unsafe to fire modern 2.75 inch shells in.
If it were mine, I'd use it for display only but keep researching it until I got some positive information on it. You may try a call to a company like Puglisi in Duluth and just ask if they would be kind enough to give you some idea about the gun. These guys live and breathe old side by sides and may be willing to chat if you don't take a lot of their time. One thing I've learned about the old doubles is that most of them were pretty junky and cheap, because fine guns have always been expensive. Another thing I've learned is that side by side project guns can get very expensive very fast.
