Googling ratskin mostly turns up roleplaying games, with creepy science experiments a distant 2nd.
However:
Apparently Charlemagne would often wear ratskin, as it was a Frankish custom: Daily Life in the World of Charlemagne - Pierre Riche, Pierre Riché, Rich& - Google Books
while modern day it is possible to get ratskin cellphone cases: http://www.wirelessground.com/mov3racabugu.html