Rotating bookmark
Rotating bookmarks were a special kind of bookmark used in medieval Europe. They were attached to a string, along which a marker could be slid up and down to mark a precise level on the page. Attached to the marker was a rotating disk that could indicate the column (usually numbered one to four, indicating the two columns on the left-hand page, and the two columns on the right-hand page).
About 30 such rotating bookmarks have been recorded in libraries in continental Europe, and another half a dozen in England.
References
- J. Destrez, L’outillage des copistes du XIIIe et du XIVe siècles, in Aus der Geisteswelt des Mittelalters, Martin Grabmann festschrift, 1935, 19–34
- R. Emms, Medieval Rotating Column-Indicators, Transactions of the Cambridge Bibliographical Society, XII, 2001, 179–l-84).