Richard Kaufman, in Steel and Silver reports that Dai Vernon told him the idea of using the thumb to flick or kick a coin secretly across the table was used by T. Nelson Downs in the 1930s, though never published by him. He used it in the context of an Unlimited Coinage of Silver routine. The first instance of the idea in print, using a cup instead of a coin, seems to be in a Larry Jennings trick in the May 1970 issue of Genii. Mike Rogers returned it to cards and coins in the May 1972 issue of Kabbala.