I am new to this forum, so forgive me if this has come up before, but a search could find no discussion of this unusual helmet. Outwardly it appears to be a German M35 Stahlhelm, but without the vent bushings. Internally however, the liner is based on the British Lining Mk.II, except, it has clearly been made especially for this type of helmet, it is not a liner from a Mk.II helmet that has been cut down and stuck in a Stahlhelm.
The helmet is made from magnetic, not manganese, steel, and weighs 1.25 kg, it measures 284x228x155mm, so roughly it is the same size and weight as a size 64 M35. The colour very closely approximates that of a war-time helmet issued to the German Army (see the comparison shot of the Briitsh Stahlhelm beside its German equivalent.
These helmets do crop up now and then on ebay, I found my own example in an antique store in Winnipeg in 1993, I know an (unprovenenced) example in the Canadian War Museum and one or two other collectors who have examples. So who made these helmets, and why?