Mills bomb

Standard British hand grenade from World War I until its withdrawal in the 1960s.

The Mills bomb consisted of a cast-iron body filled with explosive and a central tube into which a detonator, fuse, and percussion cap were inserted. Above the cap was a striker pin, held against a spring by an external lever which was locked in place by a split pin. The user gripped the grenade so as to hold the lever depressed and withdrew the pin. As the grenade was thrown, the lever flew off and the spring drove the striker against the cap, igniting the fuse and detonating the grenade four seconds later.