This is an excellent trick for beginners.
The magician displays a regular Bic pen, stating that it is a “magic rating pen” which rates people on a scale from one to ten. He then places a penny on the back of a spectator's hand, stating that “this is a one…the lowest you can possibly be.” With just a tap of the pen, the penny then visually changes into a dime..the spectator must be a perfect ten!
As a bonus effect you can also change a penny into a much smaller penny. It's very cute. This is a wonderful pocket trick that is very easy to do.