A newbie chiming in here--I see this conversation started May, 2016, but it's new to me. I will repeat what has been better said by others: WOW, what an incredible helmet!! When you come across relics in such perfect shape & they pass the "maybe it's fake" test, it's almost too good to be true. It's as close to time travel as we'll ever be able to do. To hold in one's hands a historical artifact that has been spared the ravages of time, is truly an experience.
When you spoke of your reluctance to even blow the dirt off of it reminded me of a similar dilemma that I faced with a M1916 Stahlmelm that I now have & will be the subject of a future post. This M1916 was in very good shape & even had the original M1891 picklehaube chinstrap. The original hand applied camo paint was intact, except a previous owner, who was also a total idiot, had taken an aerosol can of gloss green paint and added to the camo finish in several places. It literally made me sick to my stomach. How could I ever restore this treasure, without ruining the original paint? While complaining to a friend about this, he told me of an idea that he had seen, and it worked miracles.
In the USA we have Harbor Freight tool stores that sell cheap, imported tools. They sell a pistol like, hopper fed, sand blaster that when used with compressed air you can sand-blast rust or paint off of whatever you want to paint. My friend said, don't use sand, use household baking soda instead. I bought one of the sand blasters, masked the M1916 so the liner would not be damaged, and very timidly experimented with different air pressures & with baking soda in the hopper. Amazing!! Carefully I was able to slowly remove microscopic layers of that horrible gloss green enamel until only the original WW 1 paint remained. Later I took the M1916 helmet to a collector's show and showed it to one of the most advanced collectors in our area. He told me that my M1916 was one of the finest that he'd ever seen & the original camo finish was superb. I had to agree, but did not tell him how it was saved.
So this is a trade secret that now you guys know. A hopeless mess can be saved without destroying the genuine original.
I added one picture below. More at future date.