Reportedly, 1,022 of these carbines were manufactured by Springfield in 1855-1856. They are the only Model 1855 series arms not equipped with the Maynard primer system and were also typically .54 caliber rather than .58. The barrel has blade front and three-leaf rear sight (absent leafs, modified), a ring on the bottom attached with a swivel mounted ramrod. No proofs or markings visible on the barrel. The lock has the federal eagle motif over "US" at center and "SPRING/FIELD/1855" at the tail. The trigger guard has the distinctive large sling ring on the rear of the bow. Aside from the brass forend cap, the furniture is iron, and the buttplate tang is marked "US".