To start the fuse, the user has to pull the safety pin, then push off the cap on top of the grenade.

Right before throwing, the user has to move the switch on the lever away from the grenade in order to start the fuse.

When American forces entered World War I, they lacked a fragmentation grenade of their own.

They were manufactured for a brief time during World War I to train troops on how to initiate and throw the Mk.

Early in the United States’ entry into World War II, a number were produced as training aids in 1942.