Collectible coins are specially minted coins that often hold value beyond their face value due to their rarity, historical significance, or unique features. In the United States, 25-cent coins, known as quarters, are part of various series, including state quarters and America the Beautiful quarters. Proof sets, such as the 2014 Proof Set, feature coins struck with a higher quality and finish than standard coins, typically displayed in protective cases. These sets are appealing to collectors seeking aesthetically pleasing and limited-production items.