Quite valuable are books printed before 1500. Gonzaga University owns three of these, called incunabula from the Latin word for "cradle" because they were printed in the "cradle days" of printing. The Bruno Psalter of 1475 is the oldest printed book (incunabulum) at Gonzaga.
The University’s other two incunabula are from The Gonzaga Collection: The rare Roman Missal of 1484 records the pre-Tridentine Latin liturgy. Gonzaga owns one of only two known copies outside the Vatican. This volume is currently accessed by temporary code M58 and is not yet on the electronic catalog.
Fifteenth-century printers often recycled old manuscripts by using leaves cut from them in lieu of end-papers: The 1490 Summa Theologica by Antoninus is all the more valuable, for instance, because it has manuscript leaves from 1290 as its "paste downs" (A42). This volume is currently accessed by temporary code A42 and is not yet on the electronic catalog.