U.S. Model 1873 Cadet Bayonet.  The cadet bayonet is a scaled down version of the M1873 regular bayonet.  The blade measures 16", 3" socket with a inside socket diameter of .725".  The socket is bent downward a bit, metal shows a dark age patina, wear.  These fit the Model 1873 Cadet Rifles that were used in Westpoint, etc. Only 22k were made of these.  US faded stamp on the ricasso area of the blade.  Comes with collar ring and screw.  See photos