In the context of collectible coins, "Patterns" refer to coins that were produced as experimental or prototype pieces, often to test new designs or technologies. The United States Mint created several patterns in 1866, featuring various designs intended for potential circulation. These coins are typically struck in limited quantities, making them highly sought after by collectors. The 1866 patterns highlight the evolving nature of coin design in the post-Civil War era, reflecting both artistic and technological advancements. Collectors view these pieces as significant historical artifacts due to their rarity and the insight they provide into the minting process of their time.