Collectible coins refer to specially minted or historical coins that are sought after by numismatists and hobbyists for their rarity, condition, and historical value. In the United States, coins such as the 2007 Philadelphia Mint dollars, which may include designs like the Presidential dollar series, are collected in rolls of 25 coins. The value of collectible coins is often determined by factors such as mintage, demand, and the overall condition of the coin, with uncirculated examples commanding higher premiums. Collecting can encompass a wide range of types, including commemorative issues, bullion, and coins with particular historical significance.