These concrete egg-grenades were an improvisation that was made at the end of WW2.
It held a HE-charge and could be fitted with the
BZE fuze and detonator No.8
There appears to be a large variety in molds.

Shown below are photos © Dr.Ruby
These grenades are 200gram and 225gram, Length: 73mm and 78mm.

Photos & data below © Greg, Poland

Length: 75mm, Diameter: 58mm. Empty weight: 250gram