Collectible coins encompass various types, including historical, commemorative, and error coins. In the United States, fifty-cent coins, such as the Kennedy half dollar and the Franklin half dollar, are popular among collectors. Counterstamped coins, which have had a design or inscription added post-minting, can enhance a coin's uniqueness and collectibility. The year 1806 may refer to early U.S. coinage, such as the Draped Bust half dollar. The designation "N A" might indicate a specific categorization or authentication within the numismatic community.