Decretales Gregorii. 'Mirror image' offsets of pages removed from this book and now part of MS B 1328. A bifolio of the original manuscript was pasted down over each board: front board therefore has offset of ff 3v and 6: fragments of 3 motets with one by Philippe de Vitry; back board has offset of ff 4 and 5v: fragments of 2 motets.
See also Lerch's reconstruction of these and other fragments as 'F-CA(n)'.