Some special Allgemeine SS units used a 'transitional' type (between the M1918 and the M35) that had the shell shape of the WWI helmet and the liner/chinstrap of the WWII type. You won't see actual Wehrmacht troops wearing WWI helmets- they continued making the WWII shape even into 1945 (there was in fact an M45 helmet). I've only seen the WWI type in used by Volksturm 'troops'...
Let him who is without sin cast the first stone.
Pluralitas non est ponenda sine neccesitate- "Entities should not be multiplied unnecessarily'' William of Ockham