Sundog said:
I don't know. If I ever see a magician, regardless of his skill, turn an ordinary deck of cards into one of all the same face, I'm going to react with "I know how he did that." Once you know how it's done, the skill with which it's done seems irrelevant.
That's a good point. Changing all the cards into the same face is a tip-off to a Svengali deck. Because the effect would cause many spectators to think "Svengali deck," not too many professional conjurors do this trick.
The Mark Wilson stamp book trick is a variation of this very trick, however, and people don't think "Svengali deck" when they see it, because it doesn't involve playing cards. (Mark Wilson and his son Greg have also done a card trick in which a deck of cards all appears to be the same card, but there are various twists in the trick so that the audience will not think "Svengali deck." And, technically speaking, I don't think they used a Svengali deck to accomplish the effect.)
There is an account in an old issue of Skeptic magazine about James Randi performing a mental feat that knocked everyone's socks off. By a complicated procedure, three people found three words in books, apparently at random. They all stood, and they were supposed to be seated if, and only if, Mr. Randi said the word that they had found. Mr. Randi promptly uttered all three words, and all three people promptly sat down. How had Mr. Randi done it?
Well, according to the account, part of the word selection process involved selection of a card from a deck of cards. By forcing a particular card, Mr. Randi forced the three people to find pre-selected words according to the complicated procedure. And how had Mr. Randi forced the card? "I used a TV magic deck," he said, shrugging. It would not surprise me one bit if he used a Svengali deck to accomplish the force. If so, here was a simple card trick masquerading as a fantastic feat of mentalism.