Just back from Rare Book School and I (Sarah) want to share the link for an interesting provenance resource. The Consortium of European Research Libraries has developed a forum where you can post images of mysterious inscriptions, library stamps, bookplates, etc., and let the world of researchers comment.
(Click on “Login” to create an account.)
The site, like CERL itself, is very Western-dominated. But why not mix things up with a few Byzantine/Greek provenance questions? And, of course, a lot of Greek manuscripts are held in Western collections.