The VMS ink is NOT iron-gall

[oshfdk]

Yes, but that is what the article I quoted said too: iron-gall ink remains opaque up to 1200 nm, while ocher becomes transparent by 800 nm.  And the VMS ink is already transparent before 940 nm (the longest wavelength used in those images).

As I understand it, the article I quoted states the opposite - iron gall ink becomes already transparent at 900nm. In any case, I think I've found above three different sources that present findings contradictory to the claim that becoming transparent before 940nm is not possible for an iron gall ink.