There were thousands of inexpensive shotguns imported into this country in the later half of the 19th century, most of them came from Belgium. In addition, domestic manufactures made store brand guns for various hardware stores.
Without a name of some kind on it check for proof marks. There are a few sites on the internet that list proofmarks by country of origin, but without seeing it I would guess that it came from Belgium.
Just a quick precautionary note, damascus barrels are not very strong and were never designed to shoot smokeless loads. Since these guns were generally not of the highest quality, I would never shoot one, even with blackpowder. There is too much of a chance that even if the barrels look good, there may be imperfections in the metal and it may be a grenade waiting to go off.