U.S. Soldiers of the First Army in northern Tennessee prepare to advance against Confederate troops who have been attacked with poison gas. Circa Summer, 1916.
Broken Faces of Dixie: Disfigured Confederate Soldiers of the First Great War
If I ever have the cash, I would love to start a collection of WWI and WWII helmets of both sides.
According to the dude I talked to, and somewhat ironically, genuine Wehrmacht helmets are damn near impossible to find in Germany, as they were all recycled into other things or re-purposed for various fire brigades and eventually tossed in the 90s.