Until recently, scholars have always assumed that David Fallows's A Catalogue of Polyphonic Songs, 1415-1480 was assembled as a complete print by a single compiler working over a short period. However, closer codicological examination (see photo) reveals that it is actually made up of many individual gatherings of widely varying size.
Could the book have originally circulated as a series of independent "fascicle-catalogues" each dedicated to a single country or even letter of the alphabet?1 Until we learn more about this distant era of catalogue production (or OUP removes it from OOP), we will never know.
1 Hamm, Charles, and Eggs, Green, "Catalog Structure in the Dufay Era," Acta Musiconographica (1964), pp. 166-84.