The signature of a nun on the first page of Cape Town, South African Library, MS Grey 3c23 made it possible not only to determine the provenance of the manuscript, but also to locate two similar manuscripts in France and two in Yugoslavia. All of these manuscripts are antiphonaries for Lauds and Vespers written for nuns at the Charterhouse of Mont-Saint-Marie, at Gosnay near Arras in France. They are the only extant Carthusian antiphonaries for Lauds and Vespers and had been written for Mont-Saint-Marie because the nuns of that Charterhouse sang only those Offices. All are dated around 1540. The antiphonaries conform to the Carthusian liturgy. There is no great divergence between the music in the five manuscripts and in the Carthusian antiphonaries. Small differences exist, however. These are not the result of error, but prove that no general exemplar existed for the music of the Carthusian antiphonary.