Rick is spot on with his ID.
Just a little more information.
The first mechanical fuze developed by the Japanese Navy, with the assistance of the Hattori Clock Company, was the Type 89 Mechanical Time Fuze in 1930. The subsequent improvements to this fuze resulted in the Type 91 fuze variations, Type 0 fuzes, Type 4 fuze variations and of course the Type 98 Mechanical Time Fuze.
Improvements of the Type 89 MTF resulted in the the Type 91 MTF and the very common Type 91 Modification 1 Fuzes. Improvements on this fuze to suit different operational requirements resulted in the Type 98 MTF in 1942, the Type 0 MTF in 1943 and the Type 4 MTF in 1944
The Type 98 MTF was designed for use with the 100 mm Type 98 High Velocity 65 calibre naval gun "六五口径九八式一〇糎高角砲". It was subject to greater acceleration and rotation, so the clockwork mechanism was strengthened by using super duralumin instead of brass for the gear wheels, and the weight of components that functioned due to inertia was decreased.
A special safety flash gate was incorporated in the bottom of the fuze in place of the delay fitting of the Type 91. This, among other things, improved the accuracy of the fuze.
The Type 98 MTF had a more pointed ballistic cap than the Type 91 to conform to the ogive of the projectiles it was used in.
Cheers,
Robert
