Collectible coins are specially produced coins issued by governments or mints, often featuring unique designs, finishes, or compositions. In the United States, 25-cent coins (quarters) are popular among collectors, particularly those from Proof Sets, which are struck with a higher-quality finish and typically feature a mirror-like surface. The 2018 Proof Set from the United States Mint includes the quarters portraying national parks and sites, making them appealing to both numismatists and general collectors. These special editions are often sought after for their aesthetic appeal and potential for value appreciation.