If you ever do a second edition of the 20/20 deck it would be cool for magicians to give it a few more different markings. The deck could be stacked in Tamariz Order. Then the second “mark” down could indicate what the previous card is in the stack. And the third mark down would indicate what the next card is.

It would also be nice to put some sort of subtle mark on one end to make the back a one way design. It could be something like making one of the four inside corners of the border ever-so-slightly rounded.

One use for knowing the previous card is… The magician riffles Dow the deck and asks the spectator to say “Stop”. The magician lifts up the portion of the deck and without looking at it shows that bottom card to the spectator. As he does that he sneaks a peak at the back of the card that was in the portion of the deck that was left behind. Now he knows what the card being shown to the spectator is.

Just a thought. There are several marked decks on the market that are marked this way.

/dn