Mountineer, WW1 indeed..but not a WW1 paint finish !..a photograph of the interior would help, but IMO it is an Imperial German Model 1916 helmet shell, it looks to have had its chinstrap lugs removed and filled/welded up, (the circular mark on the side of the skirt), it looks to have a stepped lug (vent bolt) indicating a size 62-64 shell. The shell will/should be marked on crown (inside) with a heat lot number and a maker mark on inside of skirt near to the visor dip, for example "ET64"....check. As for the colour and green band I have no idea ! but with the original chinsrap lugs removed it was probably fitted with a later liner and used for some other purpose.
Prost 1 Steve.
"The German Army is the perfectly adapted, perfectly running Machine. The difference is that the Germans are organised with a view to War...with the cold, hard, practical and business-like purpose of winning victories."
G.W. Steevens - The Daily Mail (1897)
Im wondering if it could be one of the trasitional helmets used between wars to umpire manouvers, i seem to remember something about different colour bands being used
I don't really know what the green band is for, but perhaps it had something to do with training maneuvers?
Looking for WWII U.S. dog tags