Mills Bomb, Square slot filler plugs

[BMG50]

Found these near a old grenade range, very unusual where most grenade bits found are Brit or Canadian with the usual straight slot. Although the New Zealanders and Austrailians were in the area, I have seen these on New Zealand grenades, what was a common NZ base plug used with these square slot plugs.

 

[Scout Sniper]

The Canadians do use screws with a square drive, called Robertson screw.

May not be relevant, but i would suspect they are Canadian. Not many other countries ever adopted the Robertson screw drive system.

 

[BMG50]

Thats interesting, the Canadians used these filler plugs.