This is one of only ten copies known of the second book to be printed by the system of movable metal type, the first being the Gutenberg Bible, printed in Mainz 1453-5. The Windsor copy is one of the six surviving 'short issues'; the Psalter was printed in two lengths, the longer ones (of 175 leaves, of which 4 copies survive) specifically for the diocese of Mainz, the shorter ones for more general use. It is also the first book known to have been printed in red and black. This was done with a single pull of the press, the type to be printed in red having been inked separately from the black and reinserted into the same forme (the locked frame holding the prepared type). This process meant that the two colours would be in perfect register, without any unsightly overlaps. The large two-colour initials (e.g. the large initial C) were printed from woodblocks by a similar method, the block for the letter being separable from the block for the surrounding pattern. By contrast, the large blue, red and black capitals (e.g. the blue E in Ecce iam noctis, f. 97v, or the red N in Nocte surgentes, f. 98r) were inscribed, as were some of the rubrics (words in red, usually instructions to the celebrant, or catchwords to help him find his way about the page). The music, and the words to accompany the music, were also added in manuscript. The scribe responsible wrote a beautifully even hand, which has been suggested as the model for the type, so closely do they correspond.

Printed in Mainz by Johann Fust and Peter Schoeffer.

Catalogue entry from Royal Treasures, A Golden Jubilee Celebration, London 2002