From:
http://www.houseofmagicuk.com/houseofmagicuk/Customer_ProductsByCategory.asp?intCatalogID=7&page=12&strCatalog_NAME=Card%20Tricks
Cost: £14
Effect:The magician tells a story about always being beaten at cards by his Grandfather, a retired riverboat gambler. He explains the old man was able to win by using a unique marking system for the cards. The magician offers to show how effective the system was and removes the deck of cards. He explains that the reason his Grandfather was never caught using the system was that he had marked the cards on the front instead of the back. Peering at the face card on the deck the magician pretends to be looking for the mark and then announces the card.Shuffling the cards and looking at another face he anounces another. Naturally the spectators are unimpressed as they too can easily see which card is which. The magician suggests that one of them try to name a card also and is amazed to find the volunteers is right on their first try. At this point, sensing that the spectators are unimpressed, the magician explains that he has made what he considers to be an improvement to the system by adding some extra marks to certain cards. He explains that the marks can be sensed by certain gifted people. Believing the spectator who correctly named the card to have this instinct, he hands the deck with the request that they look through the cards and remember one. Taking back the deck, the magician asks the spectator to name the card they thought of. He retrieves the named selection and turns it over to reveal a red back with a bold black mark depicting the number and suit of the card. Just as the applause is about to break out, the magician goes on to explain that as some people have trouble seeing the mark he has taken this one card from another deck, the other cards are turned over revealing all blue backs.
The above is the suggested routine, I do it a bit differently, but basically after taking away all the patter, you have a deck of cards that you show the spec and ask them to choose any card freely and tell you the card. You then hand the card to them ( if you've given them the pack, you first need to take the pack back ) and upon turning it over they discover it is specially marked and a different colour to all the others.
There are no sleights and instant re set. No counting and it can be a different card every time. Pack can not be examined, but you do show it them quite thoroughly and if you follow the suggestion they even handle it at one point. ( I haven't been brave enough )
Very powerful effect really leaves them amazed. Very easy to do, not cheap but better than a lot of other tricks in this price range. It is on bikes and you can choose your colour.