This palm position for a coin, along with instructions on how to maneuver a coin into the position in the action of a one-handed coin vanish, appears in the November 1914 issue of The Magic Wand, Vol. 5 No. 3, p. 36, where the author, C. H. Shortt, attributes it to Henri Herrmann, from whom he learned it thirty-seven years earlier. This vanish includes a recovery of the coin from the rear thumb palm by the other hand, and a final display of both hands apparently empty, in which the concealment now known as the Ramsay Subtlety is used. Shortt states that he based his description on notes he took at the time he learned the sleight from Herrmann, which suggests his dating is reliable. This would make the time 1877.
Published descriptions of the rear thumb palm prior to Shortt's, although not preceding his dating of the sleight, are found in Carl Willmann's Der Zauberwelt, Vol. 5 No. 12, Dec. 1899, p. 183, where it is credited to Dr. Avon (Arthur Kollmann); T. Nelson Downs's Modern Coin Manipulation, 1900, pp. 43 and 56; Mahatma, Vol. 4 No. 1, July 1900, p. 380; and in Ellis Stanyon's Magic, Vol. 1 No. 1, Oct. 1900, p. 3. (In the Mahatma article, the source of the sleight is stated to have come from Willmann.)
However, apparently preceding all this came J. N. Hofzinser, who is said by Ottokar Fischer to have used the rear thumb palm in his routines “The Training of Money” and “Vision of a Madman” (Miser's Dream) in the mid-1800s. See Fischer's Zauberkünste, 1942 (posthumously published), p. 40.