Collectible coins, including those from the United States, often encompass different types such as Proof Sets, which are specially minted with higher quality finishes for collectors. The 1997 Proof Set, for example, features coins produced with polished dies and planchets, resulting in a reflective surface and sharp details. These sets typically include various denominations, including the iconic 1-cent coin, also known as the penny. Collectors value such sets not only for their aesthetic qualities but also for their historical significance and potential investment value.