I have already modified the original post to include this new information, but I think it deserves a message of its own.
Thanks to u/lunageek520 I was able to find Bashford Dean’s “Helmets and Body Armor in Modern Warfare” which at page 141 talks about this model and also corroborates the...
I acquired this helmet approximately five years ago through Stevanin, a reputable Italian militaria seller. Thanks to research online and to Floyd Tubbs and Robert Clawson’s book Stahlhelm, I learned that it is not a standard production piece, but rather a prototype manufactured in extremely...