The truth is more prosaic than suggested!  Paper makers weren't
wannabe Schumanns, making musical jokes with the letter H.  According
to A.W.J.G. Ord-Hume, Hupfeld's paper was made by Hoffman & Engelmann,
of Neustadt-on-Haardt.  It was watermarked with the maker's initials
and the date the paper was made.

A fair degree bit of leeway should be allowed when using this to date
the roll, because paper was left to mature for some time before use.
Although H&E paper was apparently used by other makers, it's not seen
on many other makes of piano roll.  I have one Spanish "Armonic" roll
that uses it.

Hupfeld liked the product so much that they bought the company. After
this, the paper is watermarked Phonola.

Julian Dyer