P-VIsc (Vimieiro) Santa Casa da Misericórdia, Arquivo SCMVI 0248
Some annotations and alterations have been added between lines most probably by a user of the antiphoner from which the bifolium was taken: the verse Zelus was replaced by "avertantur retrorsum et eru[bescant] qui cogitant mihi mala". These annotations suggest correction and re-ordering of the chants. Also some alteration to the notation (antiphon Deus).
PEM team data (measurements and dating)