Born under Wilhelm II, getting back to medieval helmets, the "Pickelhaube" gave the soldier a "gothic" look. The point had to protect the soldier from saber hits, by deflecting the blade. The hole allowed air to go trough the helmet.
The 2d regiment had a special plate, and the 6th one had an helmet made of brass, with iron brackets.
The bowl and the neck guard are made of polished steel. all the other pieces are made of brass.