For many years, identification tended to be visual, based predominantly on the structure of pores such as hair follicles in the skin.
This could be combined with evidence as circumstantial as the bindings being of subjectively poor quality—taken as a sign the skin used was acquired through suspicious means.
The first book confirmed as authentic through its use was in 2014; it was a copy of Des destinées de l'ame by the French philosopher Arsène Houssaye, held in the Houghton Library of Harvard University.
Such cases are further complicated by requests by descendants to return such books to the families, after which they may be buried or destroyed before they can be tested.
In her book Dark Archives, the anthropodermic bibliopegy expert Megan Rosenbloom connects this to changing standards of medical ethics and the relatively recent emergence of the concept of consent in medicine.