I am indebted to Jan Forster who I saw at Michael Murrays MINDS convention in Newcastle upon Tyne, UK in July 2017. He included this routine in his lecture and he has kindly given me permission to include his routine with the dice sets you need for it.
The mentalist hands a large envelope to the audience. Then he asks another person to come up on stage, preferably someone that is familiar with playing cards. The volunteer unpacks a sealed pack of cards and removes the cards leaving them in the new deck order to make it easier to find the cards later. The effect is done by the spectator on a small table, the performer doesn’t touch any of the cards ever. The audience is then asked to call out cards that the volunteer has to remove from the spread. Once they call out 6 cards, the remainder of the cards is placed back in the box – the spectator is allowed to keep them. The volunteer holds the 6 playing cards. The performer never touches them. The assistant places the 6 cards face down and mixes them around on the table. Then using a felt pen, the volunteer numbers the cards 1 – 6 as he chooses on the backs. Each card is now numbered (coincidence?).
If the audience were to now call out a number from 1-6, this would not be enough of a coincidence. So the volunteer is given 3 dice, and tests them first by rolling them in order to show that there is no magnet or heavy point of the dice. Once the volunteer is sure the dice aren’t gimmicked, the routine continues.
The rules of the game are first determined, then the elimination of 5 of the 6 numbers begins, until coincidentally (are there coincidences?) just one card remains. Whatever number the assistant rolls, the corresponding card is removed. After a short time 5 cards are eliminated (using 3 dice that goes quickly). One face down card coincidentally remains, and only the volunteer is allowed to see it. The performer then retrieves the envelope from the audience, from which he removes a giant card, and only shows the reverse side. The empty envelope is returned to the audience so that they can check that the envelope is completely empty. The volunteer now names the coincidence card and shows it to the audience – let’s say, for instance, the King of Hearts.
The performer turns the giant card around – it is also the King of Hearts…