"[1] Through his pioneering studies of watermarks, Stevenson solved "the most fascinating, and perhaps the most notorious, bibliographical problem of our time,"[2] the dating of the Missale Speciale or Constance Missal, an undated incunable (book printed before 1501) believed by many to pre-date the Gutenberg Bible (c. 1455), and possibly to have been the first printed European book.
The screen would usually have attached a design made of copper or brass wire which would leave a slight impression or watermark in the sheet of paper.
In early 1954, the Pierpont Morgan Library (now the Morgan Library & Museum) announced the acquisition of a copy of the Missale Speciale, or the Constance Missal, a rare undated incunable printed from the same type used in the 1457 Psalter printed by Johann Fust and Peter Schöffer, but seemingly in a more primitive and unfinished state.
[10][11] The Morgan Library and many bibliographers believed the Missale Speciale pre-dated the Gutenberg Bible and was the first European book printed using movable type,[12] basing the belief on the work of Otto Hupp around 1895.
[13] Hearing of the Morgan's acquisition, Stevenson began an analysis of its watermarks, and initial work quickly led him to conclude that the paper dated from the 1470s.
[17] In his works on the Missale Speciale, Stevenson addressed the relationship between the presence of specific watermarked paper and the date of printing, and developed the principle of "runs and remnants".
In contrast, the presence of a single or few sheets with a particular watermark (a "remnant") might reflect an older paper used, and not be indicative of the actual printing date of a book.
In part because of their sometimes crude appearance, it was widely believed that block books dated to the first half of the 15th century and were precursors to printing by movable metal type, invented by Gutenberg in the early 1450s.
[26] During his life, Stevenson achieved little formal academic recognition, taking twenty years to get his doctorate and never obtaining tenure as a professor.
[27] He is seen, however, as a major figure in the history of bibliography for his groundbreaking work on watermarks and their uses, and his Problem of the Missale Speciale has been called a "bibliographical masterpiece".
[30] In a highly technical study of early printing, for example, he gives the twin bull's head watermarks names like "Wideface" and "Squareface", using "Dick Tracy lingo",[31] and then playfully traces them through various incunables as they deteriorate and "age": Stevenson's working papers and notes are held at Princeton University's Firestone Library[33] and at the Fondren Library at Rice University,[34] which also holds Stevenson's collection of books on the history of paper and watermarks, donated by his wife in 1986.