Nice piece. I have seen Prussian cork helmets but never with the metal trim both around the front visor and read neckguard. That is certainly fairly unique.
There is no metal trim around the rear neck guard (visor) on this helmet.
What appears to be metal trim is actually green leather which is sewn on.
A good explanation is shown here:
http://www.kaisersbunker.com/feldgrau/helmets/fgh44.htm