They are marked "Type 3 81 mm Trench mortar made in 1943, Yokosuka Navy Arsenal".
Rough cross-leveling adjustment could be made, however, by breaking the bipod support and moving the leg on the low side inward.
[2] Misfires may occur with some frequency as a result of the base of the ignition cartridge remaining in the tube, preventing the next round from seating.
The fuze has three main parts; It is made of brass with the exception of the striker-detonator assembly.
A cavity behind the nose is covered with a perforated brass disk to distribute the flash from the detonator.
For instantaneous action the plug is turned so that the flash travels directly from the detonator to the booster without passing through the delay train.
Turning the plug clockwise 90 degrees makes the flash travel through the delay-train hole prior to reaching the booster.