What is a double die penny? A double die error occurs when the die used to stamp coins is struck more than once, causing a “doubling” effect. This is a die-making error, not an error that happens during the coin’s striking process. The doubling appears on every coin struck from that flawed die. Collectors look for doubled design elements, numbers, or letters, which can be subtle or very pronounced. How to identify one Look for a clear, shifted image on the coin’s surface. The doubling is often m