WWII German Helmet Original, stamped ET 64 Medal band

This is an original World War II German Helmet, it does not have the liner inside the helmet. It is stamped ET 64 on the inside of the shell. It has a medal band held in place with 3 clips, the chin strap is not connected to the medal band I do not know the history of these helmets, I was told this could be an M18. The manufacturer is Eisenhuttenwerke, Thale, Germany.