I was only sort of half-following this conversation because I figured by now someone would have mentioned the other death masks (and remember more about them than I do)... but I don't see anything about them, so here goes.
There were actually five death masks made in the mid-90s, one for each X Japan bandmember at the time: there was a Heath death mask, a Pata one, a hide one, a Toshi one, and a Yoshiki one. I have a photo of these in a magazine (random pirated Thai magazine with a bunch of X photos from various sources), but my scanner is broken, so that doesn't help you guys much. I don't know what magazine or other source they originally came from. I do remember seeing them somewhere else, but it's been years.
I don't know if the mid-90s hide death mask is the same as the one that was in the museum or not, because the only photo of the mid-90s one I have is sort of too small to thoroughly compare.
Anyway, just some random info on the subject for you guys, though it's admittedly not particularly helpful unless it leads someone to finding photos of the mid-90s X Japan deathmasks online or something.