I'm going clarify this question as I go.
Penguin sells a couple coins that they call PK coins that will not work with Sixth Sense. It will not work with this coin:
http://www.penguinmagic.com/p/9810
The coin you need for the heads and tails routine is a magnetized coin. This means it has a magnet embedded inside the coin. Sometimes we call these PK coins.
There are coins sold by Penguin for this trick but you should be able to use a normal magnetized coin.
A magnetic coin, one that is attracted to magnets but not other metal, will not work either.
