Imperial German Pickelhaube Evolution 1842-1915
 
Ersatz Helmets
To meet with the demands imposed by the Aug 1914 declaration of war, the Germans began manufacturing helmets from Ersatz (substitute) materials. Felt, tin, steel and fiber are the most common encountered. Helmets can be found with brass and silver fittings as manufacturers used up remaining parts from pre-war helmets, and eventually M1915 grey steel fittings as the war progressed.
Ersatz M1895/97 Preußia Line Infantry Regt
Surviving examples can also be found with or without front visor trims, rear spines, or Kokarden.

Please see the Kaiser's Bunker Pickelhaube Guide for further information and examples.

This period photo of an issued M1915 Artillery utilizes M1895 brass fittings.
 
References