Originally manufactured in 1864 as a muzzle loading percussion rifle, this Springfield underwent a post-Civil War conversion to breechloader via an unfamiliar mechanism that bears resemblances to both Erskine Allen's trapdoor system (hinge configuration, firing pin arrangement) and the Needham conversion of Fenian Invasion fame (side-mount configuration, unlocked breech secured by falling hammer). Blade and 2-leaf rear sights, with 1864 dates on the barrel and lock plate and no markings on the breechblock. Smooth straight wrist stock, with faint cartouches on the left side and a "US" marked buttplate.