A sophisticated device ("selective amnesia inducer") kept by Superman in the Fortress of Solitude and useful in wiping selected memories from the minds of people. It is used in a friendly competition between Superman and Batman and Robin to see which newly-rendered "amnesiac(s)" can solve the mystery of the other's secret identity without the use of any super powers.
Batman and Robin are able to discover Superman's identity as Clark Kent, but Superman, despite the use of such tools as Telepathic Hounds on loan from Kandor, is repeatedly stumped. Because Superman seems to be neglecting some of his heroic duties, Batman and Robin pretend to fall for Superman's attempt to discover their identities using a great calculating computer, but retain the knowledge that they are "the World's Greatest Detectives" (WF No. 149/2, May 1965: "The Game of Secret Identities").