This apparatus effect—in which a large blue checker, when covered with a tube, mysteriously moves to different positions in a stack of yellow checkers—is the invention of Austrian magician Hans Trunk. Trunk came up with the trick in 1924. His mentor, Ottokar Fischer, explained the trick, under the title of “Das Blaue Wunder” in Das Wunderbuch der Zauberkunst, 1929, p. 53; translated into English as Illustrated Magic, 1931, p. 55, where it was titled “The Blue Phantom”. Oddly, Fischer did not mention Trunk. Trunk laid claim to the trick in his book, Magische Memoiren, 1943. Portions of his book were eventually translated into English and run as a series in Abracadabra in 1951. “The Blue Phantom” is explained in the Feb. 10, 1951 issue, Vol. 11 No. 263, p. 37.