Choirbook
See the description in Gaffurius Codices Online.

The manuscript, severely damaged in a fire in 1906, is currently preserved in a set of boxes (it. cassette) at the Archive of the Veneranda Fabbrica del Duomo and unaccessible to the public. The manuscript is variously known in the literature by its olim shelfmark ‘2266’, as ‘MilD 4’ (Census Catalogue), ‘il quarto codice di Gaffurio’, or, erroneously, as ‘Librone 4’ (that shelfmark refers to a different item altogether). We chose to use the abbreviation ‘I-Mfd [4]’ in the database in order to highlight its belonging to the Libroni set and make it more easily recognizable by users familiar with the Census abbreviation or the other definitions already mentioned.