I recieved this nice one from a Chinese seller, but I have no information about it.
Should be a Chinese grenade made before WW2.
Smooth cast-iron body with two holes (5mm) drilled in the "neck".
Cast in two halves, see welded joint on photo of the base.

Total height: 115mm , empty weight: 500gram.
Largest diameter: 56mm. Flat base diameter: 27mm.
Outer diameter top: 34mm. Inner diameter top: 24mm.

Francesco came with the sectional drawing shown right.
Unfortunately this documentation came without the name of the grenade.

Seems like an early version of the Type 77-1.