There are several excellent sources of information on this bayonet; Albert N. Hardin, The American Bayonet 1776 – 1964, Rollin V. Davis, Sword Bayonets 1847 – 1865, Ron G. Hickox, Collectors’ Guide To Ames U.S. Contract Military Edged Weapons: 1832 – 1906, and Thomas E. Singelyn, The S.A.B.C. Journal, Volume 12, Summer 1995.

There were 4 contracts given to Ames Manufacturing Company for the production of this bayonet.  The first contract was for 200 bayonets on December 21, 1846.  The second contract was for 300 bayonets on February 19, 1847.  The third contract was for 500 bayonets on January 26, 1855.  The fourth and final contract was for 33 bayonets on November 23, 1855.  By April 26, 1856, a total of 1,033 bayonets and scabbards were delivered by Ames.

There are three recognized types of this bayonet.

Type I bayonets were made with a V shaped fuller running down the middle of the blade on both sides.  

The initial 200 produced for the first contract plus approximately 50 produced for the second contract for a total of about 250 were produced.  The second contract for 300 had instructions to eliminate the fuller after existing stock was used up.  A letter from the Ordnance Office to Ames suggests there may have been as many as 50 existing blades with fullers.   The first contract bayonets were stamped U.S. and R.C. (Inspector Rufus Chandler) on the reverse ricasso and the obverse ricasso was stamped N.P. AMES / CABOTVILLE with no date.

Type II bayonets consist of those produced for the second contract without a blade fuller estimated to be around 250.  The second contract bayonets were stamped U.S. over N.W.P. (Inspector Nahum W. Patch) on the reverse ricasso and the obverse ricasso was stamped N.P. AMES / CABOTVILLE / 1847 with a larger die stamp.   The upper quillon disk is stamped RC (Inspector Rufus Chandler) on the reverse side.  

Types I and II bayonets used a grip and guard design that differed from the Type III in that the hand guard has quillons that turn down toward the point of the blade at the hilt.  (This difference in quillion shape described by Albert Hardin has yet to be observed.)

Type III bayonets consist of those produced for the third and fourth contracts.  Like the Type 2 bayonets, the blades are without fuller.  The brass hilt hand guards are straighter across then the downward turned Types I and II.  The pommel flat is stamped with inspector initials of A.D.K (A. D. King) and R.H.K.W. (Robert Henry Kirkland Whiteley).  The blade ricassos are stamped U.S. / A.D.K. / 1855 on the reverse and AMES MFG CO / CHICOPEE / MASS on the obverse.

The leather scabbards are trimmed in brass and they vary slightly.  The earlier 1847 and non-dated bayonets are usually found in scabbards that are more elliptical in cross section and show an outline trim line at the long axis edging at the outer margin length of the body of the leather.  The scabbards usually found with the 1855 dated bayonets have a flatter leather body without the edging line and have a thinner tip or drag.