Note: "The Modern Library of the World's Best Books" was created by Albert Boni and Horace Liveright in 1917, when they founded Boni and Liveright, Inc. (Boni & Liveright in order to publish it. At ISFDB, however, their series is called The Modern Library (Boni & Liveright) and the long name refers only to the series after purchase by Bennett Cerf and Donald Klopfer as the foundation of their own publishing business (The Modern Library, later Random House) in 1925. Series numbering is not unique. The Modern Library, Inc, reprinted some editions under Boni & Liveright series numbers ("Catalog ID") and re-used some low series numbers for new titles, certainly. Probably it used some ID for two different titles, such as a reprint of the Boni & Liveright edition for a time and a later for new addition to the library.