"Obsolete" I don't think a single line definition will work.From what I abstract from the posts and from other usage is that an obsolete chip means that it is a chip a) from a closed casino, b) a chip from an existing casino that is out of play and will not be honored at the cage. But a caveat: some casinos retain their obsolete racks and may bring them back into play while some racks are sold and transferred to other properties. On top of all this are the various state gaming rules that regulate the use of chips in play.