German helmet model M1918 "Stahlhelm". This helmet is the improved version of the M1916, the first helmet ever used in war. This was the most used model by the German army during the pre-Wehrmacht period (before 1935). So this is a model was also used after WWI, when the soldiers used to apply decals to these kind of helmet. The helmet features a steel helmet liner band with the chinstrap attached directly to the liner band, rather than to lugs on the helmet shell, as with the M1916 version, and thus lacks the rivets on the lower flare of the side skirt which were a feature of the M1916 and M1917 versions. All German helmets were made from pressed chromium-nickel steel. I am not sure but probably the chainstrap is post war.