Why would an American helmet have "Guard" painted on it?

Was talking to a collector on the telephone (he's in another state) and he has an image of a former 75th Division soldier he knew.

Anyway, the soldier has rings on four fingers (he took rings instead of Lugers) and the two soldiers behind him have slung G-43 rifles (semi-auto in 7.9 mm Mauser). They have "Guard" in white block letters painted on them.

I have not seen the photo and would like to know why a helmet would be painted with "Guard." MP's had "MP" painted on theirs. Thoughts?

I think the G-43s were prizes of war and not being used in any official capacity.