Collectible coins, particularly those from the United States of America, encompass a wide range of types, including the iconic 1 cent (1c) coins. Proof sets, such as those minted in 2006, feature coins that are produced using a special process that results in a mirror-like finish and sharp details, making them highly sought after by collectors. These sets typically include coins from various denominations and are often limited in production, enhancing their appeal and value in the numismatic market.