Roy Walton, Bruce Cervon and Larry Jennings all claimed to have tackled the idea of having two face-up cards gradually converge around a lost selection in the 1960s. The earliest published solution seems to be André Robert's “Strategy” from Harry Lorayne's Best of Friends Vol. 1, 1982, p. 321. However, in Robert's effect the sandwich cards do not travel close to each other without any perceived action, but rather with open (faro) shuffles in between the displays. The best known version (in which the cards come closer to each other magically) is perhaps Jennings's “The Searchers”, in Richard's Almanac, No. 17/18, Jan./Feb. 1984, p. 172. Walton's solution, “Pinkerton's Ladies,” appeared in Penumbra, No. 2, July/Aug. 2002, p. 2.