The performer riffles the pack to show the spectator that all the cards are different. As the cards are riffled again, the spectator says STOP and takes a card. The performer is now able to name that card without looking at it. Magicians call this a Svengali pack. The card box has the Davenport Demon trademark on it. Complete with instructions which are printed on blue paper. This suggests that the trick was made when there were shortages of paper because of WW2. Like many companies at the time, Davenports had to make use of whatever paper was available.