Hair turning white when exposed to sun. Hmmm. I had no idea.
You're on top of art in a way I'm not. It just seems that the best argument for the mask being authentic is still "it's not impossible" and that leaves me very cold. If there were any contemporary (i.e., 1794) account of a mask being made, that would be intriguing. Without it, it sounds like someone selling tickets to her waxworks. I don't blame them, I just don't trust them.