Mint marks are small letters or symbols found on coins that indicate where the coin was produced. Each mint in the United States, such as Philadelphia, Denver, or San Francisco, has its own unique mint mark. This helps collectors and historians identify the origin of a coin and can affect its value. Collectors often pay close attention to mint marks because they can signify rarity. For example, a coin with a specific mint mark may have been produced in lower quantities, making it more desirable. Understanding mint marks is essential for anyone interested in numismatics, the study of coins and currency.