||The 40mm warhead is a shape charge (H.E.A.T.) type.
The1/3 Kg Type 2 air dropped cluster munition used a wind activated screw safety for the base detonating fuze.
I believe the top symbol (Ko) is associated with the Air Service. (Translated "Flying", "Air", or possibly "Aerial")
Second line is the date: Showa 19.5 (May 1944).
the symbol in the box ?
Take a good look at the air screw cups... see anything amiss with them?