This illuminated manuscript, a gradual of large size which an entire congregation of monks could see and read as they sang in choir (just as they are shown doing in an illustration in the manuscript itself), was previously unknown to scholars and has only recently come to light. It was clearly produced for a monastery of the Olivetan order, a branch of the Benedictines with a particular reverence for the Virgin Mary - probably Santa Maria di Baggio near Milan.

The manuscript includes fine miniatures which can be attributed to Girolamo da Milano (d. 1449), known as the "Olivetan Master." They add new information on the oeuvre and style of this master, previously known chiefly for illuminations on detached leaves or cuttings. This important new discovery is discussed by the Italian scholar Milvia Bolati, who uses it to throw further light on Girolamo, on the Olivetans, and on manuscript illumination in the period between late Gothic and early Renaissance.