P-Cm (Coimbra) Biblioteca Municipal FPM-B50-07
On the verso, bottom margin: paper sticker ("ROTEIRO" nº 1039 /Receita e despeza / 1579 / 6) and stamp (Arquivo Histórico Municipal, Coimbra).
The antiphon O claviger caeli is of particular interest, since as of May '22 it is only found in CANTUS in the antiphoner Paris, Bnf Lat. 1090, from Marseille, and in a dozen more Iberian sources, including a MS from Huesca Cathedral and P-Br Ms. 28. Indeed several items for the Vincula Petri feast decidedly refer to the Aquitanian - Iberian tradition (e.g. 602611, 002660, 201288, etc...).
CORBIN, Solange, Essai sur la musique religieuse portugaise au Moyen Age (1100-1385), Paris, Les Belles Lettres, 1952
Aquitanian notation of Portuguese variety, with the lozange used both in isolation and in descending chains of notes (it may sometimes be hardly discernible from a standard square).