This coin is a unique and noteworthy piece from the Patterns & Trial Coins series, minted in Philadelphia in 1866. It features a denomination of 3 cents (3¢) and is crafted from copper. The coin falls under the category of Proof production type, indicating that it was struck with a focus on detail and mirror-like finish, typically reserved for special presentations or collectors. As a Pattern or Trial Coin, it holds a distinctive place in numismatic history as it was likely created to test designs or serve as proposals for future currency. However, importantly, this specific coin is unmarked, bearing no mint mark, which signifies that it was produced at the Philadelphia Mint, the primary minting facility in the United States during that period. While physical specifications like weight, diameter, width, and height are marked as '0.00000000', indicating that this information may not have been recorded or is applicable, it nonetheless does not detract from the fascinating lineage of the piece. Notably, the mintage is recorded as '0', suggesting that either it was never officially released into circulation or may be among the few surviving examples, which enhances its rarity and appeal to collectors. Overall, this 1866 3¢ copper proof coin is not just a currency piece but a testament to the era's numismatic experimentation, making it a significant item for collectors and historians alike. Its absence of prior mintage also adds an element of curiosity and value to this historical artifact from the United States of America.