Collectible coins are often categorized based on specific attributes such as historical significance, rarity, and condition. The United States has produced various notable coins, including the three-dollar gold piece, which was minted in limited quantities. Buffalo nickels, introduced in 1913, feature a Native American and a buffalo and are highly sought after by collectors, particularly the 1926 issue due to its lower mintage. Coins marked with "N A" typically indicate a specific grading or authentication designation within the numismatic community.