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This gimmick was invented by Bob Ostin and marketed by Davenports as “Bob Ostin's Dice Prediction,” 1953. An ad appeared in Pentagram, Vol. 8 No. 2, Nov. 1953, p. 16. Tony Corinda also mentions Ostin's clip in Thirteen Steps to Mentalism, 1958, p. 186. Ostin's clip was made with a rubber band or elastic. The model with a metal spring was developed and marketed by Robert Nelson and Syd Bergson.