Collectible coins, particularly those from the United States, encompass a wide variety of types, including the 1-cent (penny) to 50-cent (half dollar) denominations. Proof sets, such as those from 1970, contain specially minted coins with a reflective finish, intended for collectors and often produced in limited quantities. These sets typically include all circulating denominations minted that year, showcasing both the design and quality of craftsmanship. Collectors value these coins for their uniqueness, historical significance, and potential investment worth.