US MK I Fragmentation Grenade

Grenades can trace their ancestry back to the Revolutionary War with simple hollow cast balls with fuses, to the Civil War with the “Ketchum” grenades, and then finally in WWI. Many soldiers on both sides carried grenades of all types, including the Mk I fragmentation grenade. This grenade was a cast metal lemon-shaped piece with 32 serrations that would become projectiles once exploded. It has a lever, a pull ring and a cap. To arm the grenade, the soldier would compress the lever and pull the ring, shake off the top cap and throw. The lever would come off when thrown, lighting a five second fuse, and then detonating. The US military fell out of favor with this design and it was discontinued before the war ended.

It’s descendant, the Mk II fragmentation grenade, saw much wider service with improvements that carried it through WWII and beyond as the top choice for soldiers both in training and in combat.