Original U.S. WWI Extremely Rare Inert Mk. I Defensive Grenade with Original Fuse and Lever Books & Films The interior of the helmet

The interior of the helmet still has an original M31 leather liner with all eight fingers still intact

sharp gun with partial cylinder scene still present and works perfectly

This is a dummy piece and is not filled with any explosive content

the re-siting of the fuel tank and ease of transport

Original U.S. WWI Extremely Rare Inert Mk. I Defensive Grenade with Original Fuse and Lever Books & Films The interior of the helmetOriginal 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.