This grenade is a product from the last months of the war.
The body was made out of concrete, mixed with metal fragments, formed in a paper mold.
It held a 150gram nipolit charge, held under a metal cover.
The charge held a threaded metal adapter, to accept the igniter.

Height (body only) 74mm, Width 50mm.
Weight: 400gram.
BZ39 or BZ40.
30 grenades were packed in wooden cases with the fuzes and dets separate in the same box.

Some detailled pictures on the Nipolit charge that was used in this concrete grenade.
It seems to have been fitted with a type of glue. Hence the four sharp triangle grooves in the cavity.
The threaded adapter is made of aluminium.

The grenade shown right and below shows a different fixation of the fuze which is unknown by me.
It still has remains of the paper wrapping under the cover.