Now, back to identifiers, at #WAC "The Potentials and Challenges for Researchers and Web Archives Using the Persistent Web IDentifier (PWID)" (The speakers even have T-shirts branded "PWID".)
(The english-speaking Wikipedia page on PWID is not the expected one.)
An example of PWID:
urn:pwid:archive.org:2016-01-22T10:08:23Z:page:https://www.dr.dk
(from the Internet-Draft)