It is difficult to see details of your liner, but it could be original.
Have a look at this fantastic site. It is in French I am afraid but great pics!
.: World War Helmets - Casque Adrian modèle 15 :.
Let us know your own opinion based on this info.
Haha I was actually looking at that site earlier. To me it looks like the first variation of the liner with 7 tongues but It looks to be in very good condition which would be odd for a 100 or almost 100 year old helmet. I was also looking to buy it so I don't have it in person to inspect and I do not own any helmets that old to compare the quality. Any ideas if its old or new?
It is possible to find adrians in very good condition or even near mint. Even if there are less and less.
I would also check if this is a M15 or a M23. Not sure the helmet is builded in 3 parts but the quality of the photo isn't very good
It looks as though it might be a first pattern liner. First pattern liners have seven tongues and are made from a single piece of leather. Second pattern liners are made from a band of leather with six tongues stitched on to the band. But my original advice when you posted this helmet some time ago on the WW1 allies forum still stands. The picture quality is far too poor to give a definite answer.
Books published to date... 'Belfast Diaries: A Gunner In Northern Ireland'... 'A Tough Nut To Crack - Andersonstown'... 'An Accrington Pal: The Diaries of Pte Jack Smallshaw, September 1914 To March 1919'.
Looking again at the first (very bad) picture, I noticed two small holes on the left that would means that the helmet, at some point, had the "veterant plate" fixed on it.