M1910 Canteen Cover? With Waterproof green coating?

[M1CAustin]

Hi, everyone
Just bought this canteen cup and cover at the Toronto Military Show here in Canada yesterday. I only paid $10 for it and it came with a nice dented S.M CO canteen dated 1944. Any way, I was just wondering if anyone knows about the OD green coating that was, at some time, put on it. The cover is built in the same way as my 1945 dated one. My guess was that it was put on during the early Vietnam War before the 56 pattern was widely used, probably by the Marine Corps so the OD#3 wouldn't clash with the latest fashions. Any thoughts?

[SteveR]

Any bodies guess buddy.