I haven't been able to identify this bayonet as yet. It is about 1/2 the size of the Trapdoor bayonet shown for comparison. There is a serial number stamped on the flat side so it is probably a school bayonet but, for what rifle? Over all length is 12 inches and the outer diameter of the socket is 3/4 inch with an inner diameter of about 1/2 to 9/16 inch.