You are approached on the street by a scammer who is quite adept at faking retardation. He comes up to you with a packet of old coins labeled Reward! Please return to Dr. Williams, Numismatist 453-5674
Seeing as the street-person does not have the facilities to call, yet insists on trying to hand you the bag, you call the number. A person answers ( a shill ) who, surprised and thankful when you call and fully explain why you are calling, offers a $700 reward along with directions to return the coins.
He simply asks that you be good enough to give $100 to the poor guy who actually found them, which he will pay you back out of the $700. When you arrive at the abandoned lot $100 poorer, you find you are the one left holding the bag, which contains about $6 worth of slightly older or foreign coins.