The most reliable information about the Bible's date comes from a letter. In March 1455, the future Pope Pius II wrote that he had seen pages from the Gutenberg Bible, being displayed to promote the edition, in Frankfurt. It is not known how many copies were printed, with the 1455 letter citing sources for both 158 and 180 copies. Scholars today think that examination of surviving copies suggests that somewhere between 160 and 185 copies were printed, with about three-quarters on paper and the others on vellum.