Starr Model 1858 Double-Action Percussion Revolver, .44 caliber, cap-and-ball. Oddly enough, the double-action model was produced intitially, then the single-action model (circa 1863). The double-action model does not function in single-action mode.

Starr Model 1858 Single-Action Percussion Revolver, .44 caliber, cap-and-ball.