Was the same title number
ever used more than once?

The majority of the numbers in the regular series (fewer in the giants and buckrams) were used more than once.

All Modern Library titles in the regular, giant, and buckram series had numbers assigned to them. The numbers appeared on the spine of the dust jacket or, in the case of buckrams, on the spine of the book itself. When a title was retired from the series, as titles often were when they weren't selling up to expectations or the rights to reprint the title expired or for some other reason, that title's number was reassigned to a new release.

Some numbers were used quite often. "1" was used six times, "5" was used four times, and "6" was used six times. The Modern Library started in 1917, and few titles remained in the catalog through 1970 when the classic period ended.

Here, for example, are five titles that used the number "126" between 1926 and 1970:

Cabell	Cream of the Jest	1926-1939
Chaucer	Troilus and Cressida	1940-1943
Snow	Red Star Over China	1944-1952
Mead	Coming of Age in Samoa	1953-1957
Wodehouse	Selected Stories	1958-1970

A few classic titles did last, however, as did their number. For example "9," Nietzsche's Thus Spake Zarathustra, remained in the series unchanged from 1917 through 1990, the only title in the original First Catalog to do so. Other titles such as the Shakespeare series remained in print but had their numbers changed over time.

---