Collector coins, particularly in the United States, encompass a variety of denominations and types, including the 1 cent (1c) to 50 cent (50c) coins. One significant area of collecting is Proof Sets, which are specially made coins struck with a higher quality finish, showcasing details and features that appeal to collectors. The 1955 Proof Set is notable for including the 1955 Lincoln penny, a key date for many numismatists due to its production process and limited availability. Collectors often seek these sets for their historical value and fine craftsmanship.