Japanese T-91 "Knee Mortar Fragmentation Grenade c. 1931

Original WWII Japanese Type 91" Knee Mortar " Fragmentation Grenade, c. 1931. Markings on the brass fuse housing are clear, and identifiable. Has some original red paint on the top as was customary upon the grenade being filled. Original operation: This versatile grenade could be fired from the 50mm "Knee Mortar", used as a spigot launched grenade, or used as a standard hand grenade. It had a seven second delay, which was necessary for its role as a projected munition. The threaded socket in the bottom of the body is for attachment of an auxiliary propellant increment for mortar use, or a finned tailboom assembly could be used to convert the T91 to a rifle grenade. The fuze is a percussion activated delay type, started by pulling the pin then striking the cap. If used as a mortar round or rifle grenade the fuze is activated automatically when fired, the plunger being pushed in by inertia. The delay time of the fuse is too long for practical use as a hand grenade however. Since apparently it was used mostly as a hand grenade, rather than a mortar round or rifle grenade, the design was modified with a shorter delay. The new version being designated the Type 97. The fuse assembly for the Types 91 grenade consisted of a fuse housing with detonator, , creep spring, firing pin assembly, retaining cap, and safety pin. The firing pin was recessed in the striker cap, and needed to be screwed into position to arm the fuse. Upon arming the fuse, the safety pin is removed, then the head of the fuse is struck against a hard object, firing the primer and igniting the delay.