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The evolution of the Mechanical Reverse can be broken into the following components. The movement of secretly flipping cards over from the fingertips to the palm was published by Henri Decremps in Le Testament de Jérôme Sharp, 1785, p. 161 of the Hugard translation, in the context of a Card at Any Number effect. This move used no cards as cover. It was just a secret deck flop. 134 years later, Louis F. Christianer published the same turnover mechanics with a single card, but under cover of the deck, see The Magical Bulletin, Vol. 7 No. 6, June 1919, p. 55.
Tony Kardyro described the sleight as it is used today, with the initial turnover of the deck and the pinky wedge break, as “'K's' Half Pass” in his column “For Experts Only” in The Linking Ring, Vol. 19 No. 9, Nov. 1939, p. 719. (This reference was spotted by Jerry Sadowitz.)
In the following decades, both Dr. Ronald Wohl (Ibidem, No. 28, Apr. 1963, p. 36, Wohl's ms. was written between April 1957 and March 1958) and Ken Krenzel (Epilogue Special #2, 1975, p. 251) reinvented the sleight. Krenzel gave it the name Mechanical Reverse.