I saw this post this morning and said to myself to reply to it after work. Well, it has pretty much all been said and correct but I do have some things to add.
The collet that holds the ventelater cap on to the top of the helmet appears to have the color green showing under several of the holes. This on a vetilator cap and you should see the bottom of the cap. It does ventalate. The suspension system of webbing is just like the steel helmets of The 20th century. The web straps are a thick herringbone cloth or light herringbone canvas. Was that kind of cloth used in any manner by the victorian British Army? Was this even a weave used as webbing in the 19th century? How about a bread bag strap? I do not know. How is the herringbone webbing attached to the shell of the helmet? It looks like a cut was made through the inner green fabric and then what....attached to the shell with a rivit or glue? Does the webbing go through the shell and attached to the outside of the helmet to be hidden by the faux puggaree?
Look at the incisions made for the webbing on the underside of the helmet. The incisions are not symetrical with the helmet. Certainly a template would be used to mark where the cuts should be made. The incisions look like they were not well thought out and furthermore, the webbing does not even match symmetry with the human cranium! This is the type of webbing job a guy would do in his livingroom, with the helmet up-side down in his lap, and a sharp knife in one hand and a beer in the other.I will never believe that the suspension sytem was ever, ever, a product that came out of a helmet makers shop and War Departmet accepted.
Now for the helmet shell. It looks vary convincing. But the there should be a large metal lined opening when you un-screw the ventelator top cap. The metal rim lineing the hole should have a bridge across it to insert the cap to be screwed on from the inner helmet dome. Your fastener that holds the venalator cap on looks just like the threaded fastener that is on my New Zealand Police 'fiber' 1960's "bobby" helmet. I cannot explain the WD and 80 marks. I do know that collectable militaria have been faked in the United States since at least the 1960's. I have a very nice example of the Australian Jungle Carbine. They are similar to the British .303 Jungle carbine, only made in Australia. How proud I was to take it home in excellent condition, and I dreamed of other used, worn specimines fielded by stalwart "Diggers" using ladders to scale the ridgeback escarpments of New Guinea to keep the Japanese from invading Darwin. Well....these "Australian" carbines were made here in California during the massive arms importing ito the United States. Also made, was an M1 Garand Tanker Carbine to be used in the small confines of an armored vehicle. Never existed in real life. I also have a Chinese SKS carbine aparently issued only to American collectors and never the Chinese Army. I knew it was not 'real'. I just wanted to have the erzatz gun for my collection. After all, I already had a bogus Aussie Carbine to go with it!!!!!!
EDIT: To be exact on the Aussie Carbine, several trial models were produced as experimental model with 'XP' in the serial numbers. They were sold off in the 1960's as surplus and are very rare, probably less than 700 being made for trials.