As said, there was no Manhatten Arms Company. That was a "Trade Brand Name" used by several makers on shotguns made for and sold by wholesale sporting goods dealers, retail chain stores, independent retailers and importers in the late 1800s and early 1900s. The known makers were Neumann Freres (Belgium), F. Dumoulin (Belgian), J. P. Sauer & Son (German), Harrington & Richardson (USA) and Hunter Arms Company (USA). The largest seller was Schoverling, Daley & Gates a wholesale sporting goods dealer. If the gun was made in Belgium, there will be Belgian proof marks stamped on the bottom of the barrels consisting of the letters "ELG" in an oval with a crown on top. Most of the Belgian made guns were imported between 1880 and 1914 when World War One cut off exports from Europe. These guns were made using the technology and metallurgy of the times. They will have damascus barrels with 2 1/2 inch chambers designed for shells loaded with black powder and lead shot. They were not designed for modern 3 inch or magnum shells loaded with high pressure smokeless powder and steel shot. Since we can not see your gun to determine its condition, we err on the side of caution and say that it is not safe to shoot so hang it on the wall!