This is a "spike" or "push" type bayonet (falling into the "socket" category) originally designed in 1963. It attaches to the Belgian FN-FAL (Fabrique Nacionale - Fusil Automatique Legere) Infantry Rifle with flash-hider.
It is separated into two distinct model variants: the Model 1963 and the Model 1965. The differences are simple - the Model 1963 was a better-made version than the 1965 (used mainly on exports); however, they function the same.
All-metal construction; black.
I have seen two scabbard variants: all steel and all plastic.