It may interest our readers to know that the Dominican Rite Altar Missal of 1521 is now, in part, available on-line at Gonzaga University in Spokane WA. It is published electronically by their Rare Books Collection. This is a beautiful and informative presentation, with excellent digital images, one of which decorates this post.
Of special interest artistically are the woodcuts with which it is decorated. This missal, although heavily overburdened with saints days (almost to the exclusion of the Sundays of the Year!) is important because it is one of the last editions before the Romanizing reforms mandated by the Dominican General Chapter of Salamanca in 1551. Most famously, the Salamanca reforms changed the Dominican (and Sarum) practice of counting Sundays after Trinity to "Sundays after the Octave of Trinity," an oddity preserved until the change to the Roman form of "Sundays after Pentecost in the Missal of 1965.
I thank Mrs. Jamie Ballanger for calling this publication to my attention.