Prepare for this trick beforehand by dropping a dime into the right side
of the cuff on your right trouser leg. You can carry a dime there all day
without fearing of losing it.

Borrow a dime from someone and ask him to mark it in some way for later
identification. Take the dime and pretend to place it in your right trouser
pocket, actually palming it before your hand is withdrawn. Explain that
any small object placed in your pocket immediately travels down through
a concealed tube in the cloth to the trouser cuff. As proof you reach down
and extract the dime which you had previously placed there, at the same
time allowing the palmed dime to drop secretly into cuff.

Of course everybody knows immediately how you did the trick — you
merely kept the dime in your hand. So you offer to repeat it. This time you
actually leave the dime in your pocket and with an unmistakably empty
hand you remove the originally borrowed dime from the cuff and return it
to the owner for identification.