The old German spiked leather helmets (Pickelhaube) were replaced during WWI with the steel helmet (Stahlhelm) used through WWII, with its distinctive visor and flared back.
The East Germans replaced it in the 1950s with a different style in part because West German border guards were still using the old helmets[1].
Eventually the West Germans adopted a copy of the US M1 helmet, so nobody got mistaken for a Nazi and everybody could still tell who to shoot.