Ted Annemann first mentioned the idea of getting an envelope with a postal stamp that predated the actual time of a prediction enclosed within; see The Jinx, No. 79, Feb. 10, 1940, p. 516. An envelope, barely sealed and addressed in light pencil to the performer, is mailed. On receiving the envelope, now with a dated postal cancellation stamp, the penciled address is erased and the address of the intended recipient of the prediction is written. Then the “prediction” is sealed inside the envelope.
The idea resurfaced in “Through the Mail Box” by Loren Gee in the May 1955 Linking Ring, Vol. 36 No. 3, p. 95. Here, two identical envelopes are prepared, addressed to the event chairman. On one of these, a paper label is temporarily glued over the address; on the label is the performer's address. The two envelopes are mailed together. When the prepared envelope goes returns to the performer, he removes the label, so that it now bears the chairman’s address with a cancellation stamp identical to that on the second envelope. He opens the returned envelope (which was lightly sealed) and puts in a prediction. The sealed prediction is brought to the show and, during the performance, is switched for the one received by the chairman.
In Abracadrabra, Vol. 26 No. 672, December 13, 1958, p. 339. George Arrowsmith described “Vanishing by Remote Control”, wherein an item is sealed in an envelope that is addressed to the person the performer whishes to impress. The targeted person mails the envelope, putting it into the mailbox themselves. When it arrives at his home, part of the object inside has vanished. In the Dec. 20, 1958 issue, p. 360, Arrowsmith explained the method. The first envelope is addressed using vanishing ink. That one ends up being returned to the performer. He has made a duplicate envelope (having done the writing of the address on both, so they look the same) and, in that one, part of it duplicate contents has been removed. The latter is the one the person later receives in a normal mail delivery.
(These references were compiled by Max Maven.)
See also Man Who Was Not There, The.