.58 Robert's CF. 37" barrel secured by three flat spring retained bands. NSN. Bright finish, iron furniture, walnut musket stock. Single shot breechloading cartridge alteration of a US Model 1855 Rifle Musket with a M1861 three leaf rear sight, Barleycorn combination front sight and socket bayonet lug, sling swivels and an appropriately shortened swelled shank, tulip head ramrod for cleaning and clearing purposes. Lock marked with a {Spread-Winged Eagle} on the primer magazine door and stamped U.S./SPRINGFIELD forward of the door. Tail of lock dated 1858. Side of breechblock marked in two lines ROBERT'S PAT./JUNE 11, 1867. Based upon a patent received by US General B.S. Roberts, the alterations to existing rifle muskets were preformed by the Providence Tool Company. Roberts secured a contract to alter 10,000 muzzleloading rifle muskets on hand in the various New York State arsenals, but the state refused to appropriate the funds. In the end a total of 5,000 guns were altered and sold to the state of South Carolina for the use of their State Militia (later National Guard) regiments. The guns were used through the 1870s and started to be disposed of and replaced in 1879, a process that lasted until 1890. Nearly all of the alterations were preformed on US Model 1861 and 1863 Rifle Muskets, although a handful were done on Model 1855 Rifle Muskets and some British Enfield Rifle Muskets. Alterations were left both as full-length rifle muskets, with some shortened to rifle length with saber bayonet lugs added. The modification of the action left little wood in the lock area and as such the guns broke easily in that region. Additionally a design flaw meant that in some cases the ramrod had to be partially withdrawn in order for the breechblock to lower completely for loading and unloading. With only 5,000 manufactured, mostly on M1861/63 Rifle Muskets, and the inherent weakness of the design, surviving examples are very scarce, particularly using M1855 Rifle Muskets as the base. {ANTIQUE}