This gimmicked shell coin, with half its rim removed, was conceived by Jochen Zmeck of Germany to perform a very clean transposition between a gold coin and a silver one; see “Gold und Silber” in Magie, Vol. 48 No. 2, Feb. 1968, p. 367.
In the U.S., Steve Dusheck reinvented this form of shell and, in 1974, Eddie Gibson of the U.K. marketed it under Dusheck's name, as “Slippery Sam”, a copper-silver transposition that echos Zmeck's “Gold und Silber”; see Genii, Vol. 38 No. 11, Nov. 1974, p. 492.
An early relative of this gaffed coin was conceived by George Le Walke. This was described by Edward Bagshawe in The Le Walke Mysteries, 1921, p. 31. Le Walke's gimmicked coin consisted of a coin shell with half of its rim removed and a second full side of a thinned-down matching coin attached to make a hollow coin, open at one edge. This coin could be displayed on both sides while concealing another coin inside it.