This is a NZ made stick grenade, originally made by Mr Jack Smith for his Akoroa (near Christchurch on the east coast of the South Island) home guard unit during WWII, possibly made by others to the same pattern.
Made from 1 1/4" water pipe and a wooden handle.
Ignition was by pulling the spring and igniting a .22 short case with safety fuse inserted into it giving 3 seconds burn time.

As a safety measure a wooden wedge was placed under the spring and retained with string.
The handle would normally have a rougher finish, straight from the lathe.
Explosive composition is unknown.

Photos and information © Andrew Edgcombe.