This is a "spike" bayonet (falling into the "socket" category) used on the No.4 SMLE (Short Magazine Lee-Enfield) Infantry Rifles used from about 1939 to about 1957 (perhaps into the 1960s); it was the successor to the P1907 Mk1 Bayonet and the predecessor to the No.9 "Knife" Bayonet. It has no proper handle but home guard units were issued these with a "broomstick" attachment that allowed them to be used - with this extension - as a close-combat thrusting weapon.
They are very basic, yet very functional as a bayonet (useless as a knife).
They come in a number of variations but are basically identical to the British British No. 4, MkII Spike Bayonet; the main difference being the overlapping letters LB (Long Branch) and perhaps an "arrowhead" in a circle (Canadian Ownership). Some of these were also produced in the United States by Savage Arms (marked with a very squared "S", often-times in a square border). These were produced in very large quantities and the common MkII variant sells on the current retail market for under $15 with scabbard.

The scabbards are cast metal or sometimes plastic (Victory Plastics).