P-AR (Arouca) Museu Regional de Arte Sacra do Mosteiro de Arouca Res. Ms. 005
This is a supplement to the main antiphonary volumes used in the choir. The opening guard-leaf features a large inscription of ownership: Do Most[eir]o d' [A]r[ou]ca. Fol. 1 features the insignia of D. Melícia de Melo, abbess between 1511 and 1561. This choirbook has a pair, Res. Ms. 003, slightly more complete at the end.
Catalogue entry in https://arouca.fcsh.unl.pt/content/res-ms-005
Square notation in (slightly faded) black ink over red 5-line staves.