Sermones Bernardi (Tomus II). A rear guard leaf contains music; front & rear boards have 'mirror image' offsets of pages which FallowsCA suggested were part of MS B 1328 (front board = f. 7v, a motet of Philippe de Vitry,. Lerch instead considers this, and the rear leaf/board, to be different leaves from the same original manuscript. A fragment of the original front leaf remains, left behind when the page was removed. Back leaf and offset: fragment of an otherwise unknown Gloria.
See also Lerch's reconstruction of these and other fragments as 'F-CA(n)'.