Ames manufactured approximately 4,250 of these distinctive "mule ear" breech loading carbines between 1843-1846, according to "Flayderman's Guide" (9th Edition, 9B-061). The Jenks carbines were originally smoothbores with a round loading aperture. Around 1861, most Jenks carbines were rifled and had the loading aperture enlarged to an oval shape to accept a paper cartridge rather than loose balls and powder. "Wm JENKS" and "U.S.N./RC/P/1845" marked on the top of the barrel at the breech ahead of the oval loading aperture, with a rifled bore. "3/41" marked on the underside of the lever. Small "P" inspection marks are on several components. The lock plate has the Ames three-line marking in the center and "Wm JENKS" towards the rear. Sling ring mounted on the lower tang. Oval script "RC" (Rufus Chandler) and bordered script "JL" (Joseph Lanman) inspection cartouches stamped on the left of the stock.