Trick: The magician explains to the spectator that his electronic rating pen will rate them on a scale from 1 to 10. The magician places a penny on the back of the spectator's hand and explains that the penny is the lowest rating you can get. The magician then taps the penny with his pen, and it changes into a dime. The magician exclaims "Wow, You're a 10... You knew that!".
Info: Pen is an actual functioning pen.