who devoted the larger part of a folio volume to a review of the paper-marks of the block-books, undertook to prove from them that the Speculum must have been printed before 1440.
All known copies of the Speculum contain a variety of dissimilar paper-marks. Among them are the hand, the dolphin, the lily, the unicorn, bulls' heads, the letter P, the letter Y, the letters M A, the spurred wheel, and the papal keys. Many of these marks are found in the paper of the Canticles and the Bible of the Poor. It is evident that papers bearing so great a variety of paper-marks were not made at one mill, and probably not in the same district. They were not made in Holland, at least not during the first half of the fifteenth century, for there were then no paper-mills in that country. 
The early records of the treasury of the city of Haarlem, which are written on papers containing paper-marks like those of the Speculum, show that the paper was bought at Antwerp. Koning thinks that the Speculum, and the block-books which are printed on the same paper, must have been printed between 1420 and 1440; that the paper of the books was made in Brabant; and that many of the paper-marks are the initials or arms of the house of Burgundy. According to Koning, the letter P stands for Philip the Good, Duke of Burgundy, who reigned from 1419 to 1467; the letter Y stands for Ysabella of Portugal, who married Philip in 1430; MA stand for Margaret, who was countess of Holland before that state was ceded to Philip in 1433. These are very confident assumptions; they require a careful examination.
A closer investigation has elicited these facts: the letter P has been found in the accounts of the Count of Holland at the Hague for the year 1387; paper bearing the same P was used by many printers of the Netherlands, by one printer in Paris, and by several printers in Germany in the last quarter of the fifteenth century. It is found in paper made before and
