This is one of approximately 7,000 fourth model or transition type Burnside carbines manufactured between 1863-1864. Unlike the preceding models, the breech block features Isaac Hartshorn's patented improvement with a hinged center section allowing for easier loading of the Burnside cartridge. The frame lacks provision for Bacon's patent centrally located guide screw which distinguishes these fourth models from the subsequent fifth model. Matching serial number "4" marked on the breech block and frame. Initials "DEA" stamped on the buttplate.

Good, exhibits mostly smooth brown and gray patina with some areas of light to moderate pitting, and clear markings in the metal. Wood is very good as lightly sanded and re-oiled, with some scattered scratches and dents. Mechanically excellent.