Collectible coins from the United States of America include various denominations, such as the 1 cent (1c) piece. The 2009 Proof Sets feature specially minted coins with a higher quality finish and are sought after by collectors for their clarity and detail. These sets typically commemorate significant events or changes in coin design, making them valuable to both numismatists and investors alike. Proof coins are produced using polished dies and are struck multiple times to enhance their luster.