A split is a type of Faro bet. See Faro rules here, for example,:
http://www.bcvc.net/faro/rules.htm

In the gambling supply catalogs, "splits" seem to be just plain 1-1/4" chips for betting at Faro. See page 409 of the 1998 Seymour's book, and p. 257 of the old book.

Robert