Yeah, I don't know that I'd buy into the zinc fitting story. For me, a rare helmet like that has to prove itself to be original and un-messed with, which IMHO this one does not.
On the other hand, I have what might have once been a General a'la Suite on which the silver was rubbed from the eagle on front, but is still on back. One of those 'oops!' helmets I purchased when I was a young collector, long before Pick's dot com came along. I didn't have any 'Garde' helmets and wanted one! Luckily, at the time, it was less than a quarter the price of a good General a'la Suite, so it's one of those 'learned a lesson' helmets. Of course, all that's missing is the silver on the wappen... maybe someday get it re-plated.. (?)