The Slydini Switch, described by Karl Fulves in The Best of Slydini...and More (aka The Magic of Slydini…and More, 1976, p. 105), uses Slydini's Imp-Pass for the secret exchange of one or several cards. Dominic Twose points out a predecessor in print: Terry Guyatt's “Card Exchange”, described in Step 10 of Corinda's 13 Steps to Mentalism (p. 317). In response to a query from Twose, Guyatt reports that he invented his exchange in the 1950s, building on Slydini's misdirectinal techniques published at the time. Tony Corinda originally released Step 10 of his series in late 1959, roughly seven years before the Imp-Pass appeared in print in Leon Nathanson's Slydini Encores (1966, p. 25), and seventeen years before Fulves's work cited above. It is certain that Slydini devised the Imp-Pass and Slydini Switch years before their publication, although how many years before is not known. There is no reason to believe anything other than independent invention is in play here. There is a salient difference between Guyatt's switch handling and Slydini's. At the moment of the switch, Guyatt writes that you drop “the left arm below the edge of the table”. That is, the left arm and hand, holding the card to be switched out are briefly lowered partially or wholly out of sight, behind the table, when the left hand releases its card and picks up another, held by the right hand just below the table edge. The dynamics of Slydini's Imp-Pass are not in play here. In the Slydini Switch, the left hand drops onto the table, at the edge, and the cards are exchanged using the Imp-Pass dynamic. The left hand never leaves the sight of the audience, nor appears to come close to the right hand in the lap. It is fair to say that Guyatt's exchange and Slydini's switch are closely related, as both are done with misdirection, use of the gaze and with similar, natural, covering body motions.