Question about WW2 Fibre DR Lids

[Dean (Ajax)]

I have a question about Fibre DR lids...I just bought 2..both were painted white...the "taller" one has some of the "White" missing and I can see it was Green underneath..dated 1943..the interesting one is very "short"..on one side is painted a red square with a yellow Maple Leaf..and on the other side is square...top right is very dark blue..the lower left side is yellow..and the number 21 is overlaid on it...any ideas?
Were these used in Europe?

Wish I knew about this sort of thing...I bought these with a load of WW1 Canadian and German bits as well as several WW2 Canadian Officers shirts and other items...some I will keep some I will sell...but I now think some may be WW1...need to do more research

Dean