Prompts me to wonder when the term 'world war'was first used. In Britain, I'm pretty sure that the term ' The Great War' would have been used at the time and for some years afterwards - until after 1939-45? Does anybody know ?
Years ago, when I was working at the airport, one of the mechanics was using an old WWII Herring Bone Twill (HBT) Blouse for a rag. On its back was a painting of Donald Duck holding a blue sphere. I asked him where he'd gotten it. "Oh, I got that in Iceland during WWII, one of those guys who painted bomber noses did it for me."
I asked him for it and got it (the painting is in BAD shape). A former boss who was stationed the entire war at that air base said there was a Disney artist who was stationed there. I often wonder if it's from the same fellow.
I've seen a lot of nicely painted souvenir helmets, I'd take the Disney story with a grain of salt. Now if Walt himself had authenticated it and signed the paper.... It seems to me that somebody would have tried to authenticate this much earlier.
I couldn't find any pre-animation / cartoon work of his on the internet, so can't speak toward his style, but it's certain that who ever did this had a good hand.