1940 German gas mask canister-markings?

[aghsmac1]

Anybody knows what is the meaning of the markings W.P. on the canister?
It's also marked D on the bottom (WATERPROOF) and 1940 WaA309 inside.
Thanks in advance, aghs

[lebus12]

No idea, perham the name, Walther....Not Winston, of course

[aghsmac1]

It's stamped not written with hand. Must be a unit or something like that, perhaps W means Wehrmacht but what's P?
aghs