Originally developed in 1928, the Type 89 Mortar was a mainstay of Imperial Japanese forces through World War II. Lightweight, compact, and easily transportable by a single operator, the Type 89 was nicknamed the "Knee Mortar" by Allied troops due to an unfortunate misunderstanding of the design of the baseplate. Intended for use with a downed tree or similar rugged material, the smooth curvature made it a good fit for a human thigh or knee; any American attempting to use their leg as a firing platform was destined for a painful lesson in Newtonian physics (specifically regarding equal and opposite reactions) and a trip to a field hospital. Designed to be fired at a fixed angle, range control is accomplished via a threaded bolt assembly that extends through the breech, effectively reducing the barrel length as needed. A double-action style firing mechanism is integrated into the bolt, and a spring loaded canvas cover protects the bolt slot. Matching numbers are present overall.

Very good. Approximately half of the original blue is present, with areas of brown patina and scattered spotting. The baseplate shows heavier corrosion, which appears to have been cleaned up, and the canvas cover shows material loss and a loss of tension in the spring. The elevation adjustment mechanism and trigger are both in good order. NOTE: This Destructive Device is a National Firearms Act (NFA), fully transferable Class 3, which is registered with the Bureau of Alcohol, Tobacco, Firearms and Explosives, (BATFE) under the provisions of 18 U.S.C. Chapter 44 and 27 CFR part 478.