Collectible coins, particularly those from the United States, can encompass a wide range of types and denominations. A roll of coins typically contains a specific number of coins, often 50, depending on the denomination. The 2011 Philadelphia mint coins often refer to coins struck at the Philadelphia Mint, which is known for producing various circulating coins, commemoratives, and special editions. Collectors may seek out dollar coins from this year and mint location for their rarity, historical significance, or condition. These factors contribute to their desirability in the numismatic market.