I don't typically buy and sell other magician's marketed effects but I had to make an exception for this trick. It starts off as a bar bet. Then it morphs into a visual magic effect. It suits my character and resets quickly. It's a very strong piece.
A card is freely selected and signed. The magician then punches a hole in the card. A coin is borrowed and a puzzle or bamboozler is presented. Can they get the coin through the hole without damaging the card? They can try as much as they like, but it's painfully obvious the coin will not fit through the hole. First you show them the old bit where you place the coin down with the card hole on top and literally push or scoot it across the table. This gets groans.
Now for the magic! You visually stretch the hole until it is big enough for the coin to fall through comfortably and then, with just a flick, the hole visually shrinks back down to its normal size.
Afterwards, the card and coin are handed back to your spectator.
This is easy to do for any experienced card magician. It comes with hand-engineered gimmick and full instructional DVD explaining the commercial handing (simply supply your own regular hole punch and matching deck and you're set to go). The gimmick included is a red Bicycle Poker backed card.