This is a classic steel helmet of german army during WWII. This papercraft is designed by D-Mind. There is another German Helmet at this site: Life Size: WWII German Helmet (Stahlhelm) Free Papercraft
Stahlhelm is German for "steel helmet". The Imperial German Army began to replace the traditional boiled-leather Pickelhaube with the Stahlhelm during World War I in 1916. The term Stahlhelm refers both to a generic steel helmet, and more specifically to the distinctive German design.
The Stahlhelm, with its distinctive "coal scuttle" shape, was an instantly recognizable icon for military imagery and became a common element of military propaganda on both sides, just like the Pickelhaube before it.
Its name was also used by the Stahlhelm, a paramilitary nationalist organization established at the end of 1918.
You can download this M42 helmet paper model from here: WWII German M42 Helmet (Stahlhelm) Free Papercraft Download