Otto,
This helmet is a Model 1916 Stahlhelm (leather liner band and M91 type chinstrap connections). The visorless helmets for the Turkish Army/Freikorps were a variant of the Model 1918 (steel liner band with the chinstrap attached to the linerbad instead of M91 attachments).
I could not state with authority that M1916 helmets were not made/converted to this pattern, but conventional wisdom says that the Turkish contract were Model 1918s.
Although it looks nice, I will wait to see an authentic M1918 visorless helmet.
Mike