Collectible coins encompass a variety of types, including patterns, which are experimental coin designs created by mints before official production. In the United States, the term 'P3C' refers to pattern coins struck around 1850, often showcasing innovative designs and compositions. These patterns were essential in the evolution of U.S. currency, as they provided a means to test public and governmental approval before finalizing a coin's design. 1850 pattern coins remain highly sought after by collectors due to their rarity and historical significance.