Don MacArthur adds:
"The bomb is a Type 98 No. 7 Model 1 Navy fire bomb. It contained four thermite filled fire pots and a black powder charge in a recess in the nose piece. Two rows of 10 rivets each. It had 81 pounds of filling, hence the yellow powder.
Stan Gajda adds:
"The bomb is a Japanese 65kg HE aerial bomb. It seems the rear fuse exploded without initiating the main charge. They are lucky or would have blown the crusher to hell. The yellow substance is the Picric Acid explosive filling. Dust from this explosive when wet stains anything in contact with it bright yellow. I have one of these bombs in my junk in Tarawa and I have seen several casings in Nauru. The sheet steel tail fins are missing which are welded on. Probably rusted away."
Thanks Jimmy Nuake, Peter Flahavin and Ewan Stevenson