A boy is given two medals that once belonged to his veteran grandfather. One is a medal of honor, given for service and bravery in world war one. The other is a medal of honor given for service and bravery in world war two. The boy later goes to a pawn shop to see how much the medals would be worth. The owner tells the boy that, even without an expert, he can tell that one of the medals is fake. Which one, and why?