Collectible coins encompass a variety of categories, including commemorative, bullion, and proof coins. In the United States, the 2019 San Francisco proof set features coins minted with a special polished finish, particularly appealing to collectors. The set typically includes a range of denominations, such as the iconic 1 cent (1c) coin, with each piece showcasing high-quality detail and striking. Collectors often seek these sets for their aesthetic appeal, historical significance, and potential for value appreciation.