These "New Model" revolving rifles, carbines, and shotguns were manufactured in a variety of configurations from 1855 to 1864. Of the 18,300 manufactured, only 2,300 were .56 caliber carbines with 21 inch barrels. However, this carbine is rarer in that it is one of the roughly 2,000 .56 caliber carbines (various barrel lengths) with London proofs, and, unlike most of those 2,000, this one has an iron buttplate rather than the brass buttplates typically found on the London carbines. It also has a brass blade front sight, three leaf rear sight (one standing), the standard one-line address on the top strap, patent markings in one of the cylinder flutes and left side of the frame, saddle ring and stud on the left, and smooth buttstock. The matching serial number is visible on the bottom of the barrel, frame, and trigger guard as well as at the toe of the buttplate. The left side of the stock also has an old collection inventory number "2704" stamped in it.