Entering service in 1929, the Type 89 launcher was a dual purpose weapon, capable of firing both the standard Type 91 fragmentation grenade for anti-personnel work, and also the Type 89 round, which was closer in potency to a true mortar round. The knee mortar designation came about due to GI's observing that the curvature of the base plate (meant for use with a tree trunk) would make a good fit for a human leg; an observation that led to a number of injuries from the heavy recoil of the weapon. Overall length is 23 3/4", with the barrel marked with the serial number over a set of arsenal proofs, the full serial number on the barrel mounting ring, main spring tube, and base, "399" on multiple small parts, the range adjustment wheel mounted to the right of the main tube, spring loaded rubberized canvas dust cover and curved base plate.