NSN. Manufactured circa 1866–1867 by Springfield Armory, chambered in .50-70 Government,40″ round barrel. The bore shows oxidation with strong rifling still visible. The barrel has aged to a light grey patina with scattered mottled oxidation consistent with long service life. The Model 1866 represents the 2nd Allin conversion, an important transitional rifle in which Civil War-era muzzleloading muskets were converted to breech-loading metallic cartridge arms for continued U.S. Army service on the post-war frontier. The stock has been refurbished at some point and shows expected service character. The action holds at both half and full cock, though the mainspring is light.