Collectible coins encompass a variety of numismatic items, including historical coins, commemorative issues, and sedimentary pieces such as the United States quarter. The 25-cent quarter is a staple of American coinage, with many designs celebrating states and historical events. California Fractional Gold coins, minted in the mid-19th century, represent a unique category of gold coins issued to facilitate commerce during the Gold Rush. The year 1866 is significant in U.S. coin history due to the introduction of the Indian Head penny and the transition of various designs in circulation. The term "Unknown" may refer to coins without a recognized attribution, which can be of interest to specific collectors seeking mystery or rarity.

Item Denomination Series Year Mint
1866-- (Unknown) California Fractional Gold 25¢ (Twenty Five Cents, Quarter) California Fractional Gold 1866 Unknown