Bottom plugs

Hello,
I dont know how the correct translate from my native should be but maybe its correct - bottom plugs. Anyway this is the part on the bottom of artillery fuze. I have found a lot of those mini plugs together with A-H seals - propably were in sack. Two of them have signatures - M in circle and KC (Keller & Co.???). They are really small - diameter 9mm. Where they could be used? Or maybe I am wrong and its some inner part of fuze? Thanks for any suggestion.

anemon