Only a small number of these pistols were converted to this system around the late 1850s to early 1860s. The conversion consists of fitting a drum bolster and nipple to the barrel, removing the frizzen and flash pan, and replacing the cock with a hammer with a built in automatic priming system. The design was patented by George W.B. Gedney of New York. Only a small number of these components were purchased by the U.S. government. The hammer is marked "PAT. MARCH 15. 1859" towards the top and then "AMc PRIMING & ARMS Co./NEW-YORK" on the neck. The lock has the original "WATERS/MILBURY. MS./1838" marking along with an "E" stamp. The barrel has "U.S./JH/P" and "H" on the left at the breech. The stock has traces of two cartouches on the left.