Collectible coins, particularly those from the United States, can encompass a variety of types including cents, nickels, dimes, quarters, and special mint sets. The 2006 Proof Sets produced by the San Francisco Mint feature high-quality coins struck using polished dies, showcasing enhanced detail and a mirror-like finish. These sets often attract collectors due to their limited production and aesthetic appeal, making them a popular choice among numismatists. The inclusion of the 1-cent coin, along with other denominations, adds to the desirability of these sets.