The Origins of Wonder
A prototype of the Sandwich effect may be seen in Richard Neve's The merry companion: or, delights for the ingenious, 1716, p. 121; see “To make any one blow a Card in between two Cards.” In this early effect, the performer holds half of the deck in each hand and slams them together, face to face, causing an indifferent card to appear between them. The card that appears is not a selection.
An early modern example of the Sandwich effect is Louis F. Christianer's “Obedient Card” in The Magic Wand, Jan. 1917, p. 78. Note Christianer's introductory comment: “This trick is a variation of one I have performed for some time, and which has been made familiar by Malini, Merlin, and others. In their hands a good deal of manipulation is required, and the average performer does not care to bother with it.” From this it would seem the Sandwich Effect, with various methods, was in circulation at least among professionals for some time before Christianer published his revised handling.
There was also a variant in which the two reversed sandwich cards appear by surprise, surrounding the selection. William Larsen and T. Page Wright had one of these in their L. W. Card Mysteries, n.d. (c. 1928), p. 10. Jack McMillen and Judson Brown published another method for the L. W. effect, titled “A New Reverse Location” in Take a Card, 1929, p. 8.