This is the No.9 "knife" bayonet (falling into the "socket" category) successor to the No.4 "Spike" Bayonet, also used on the No.4 SMLE (Short Magazine Lee-Enfield) Infantry Rifles. These were used from about 1948 into the 1960s. It has no proper handle but could have been used with the "broom-stick" attachments issued as with the No.4 "Spike" Bayonet.
They are very basic, yet very functional as a bayonet; without a proper handle, very unwieldy as a knife. They come in a number of variations. These were also produced in very large quantities and sell on the current retail market for under $20 with scabbard.

The scabbards are sheet-rolled-steel and fit virtually all of these later British "Bowie" bladed bayonets.

These bayonets were also used by Australia, Canada, New Zealand, Pakistan, South Africa, and perhaps others.