This grenade was found in the Philippines, together with other Japanese grenades, near Clark Air Base on Luzon Island.
It seems to be an improvised type, made of steel, with a .22 caliber short case as a fuze.
The .22 shell is marked with a "U". The top fits into the body with a friction fit. There are no threads.
The inside of the body has two small steel rods welded onto one side to hold a charge.

Length : 85mm
Diameter : 45mm in diameter at the top of the body, and 47mm at its base.

Photos and information © Rob V.