Original Item. Only One Available. The Mk 1 grenade (sometimes spelled Mk I) is a fragmentation hand grenade used by American forces during World War I. According to its designers, it was to be the "simplest", yet most "fool-proof", grenade ever made. However, some major problems appeared when the grenade was used in the field. It was retired from service before the war ended, replaced in 1918 with the improved Mk 2 grenade used through World War II. Like all deactivated ordnance, this grenade is Not Available for Export.

This is the first fully original Mk. I grenade we have ever offered at IMA, as the majority of them had their bodies reused during the interwar period and WWII. This example retains its original fuse which is missing the top piece, and the original lever which is almost always missing. The body is maker-marked with a 4 above a Diamond emblem. The grenade is in good shape overall without any serious damage.

The MK 1 is a time-fused fragmentation grenade and has 32 serrations on it. 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.

To operate, the grenade was held in the right hand, the thumb crossing over the lever, the high ridge nested in the crevice of the thumb's first joint. The pin is removed and the top cap shaken off the grenade.

With an overhand throw, the lever was intended to be "automatically" twisted, by the thumb, as the grenade rolled off the palm of the hand. At about a 20° angle the lever frees the cocked striker which snaps like a mousetrap, initiating the primer and lighting the 5 second fuse.

This is a rare opportunity to pick up a very scarce WWI grenade, the first of its kind we have ever offered. Comes ready for further research and display.