What This Coin Looks Like (Obverse, Reverse, Mint Mark Location, Special Features, etc.): One major variety of the 1807 Capped Bust Half Dollar features an error on the denomination depicted at the bottom of the reverse of the coin. A "50" is struck on top of a "20" in the "50 C." denomination. It's possible that the designer accidently began working on a "25 C." die for the quarter and quickly got mixed up with the "50 C." die for the half dollar. The 50 was then struck over the 20 after the mistake was found. Parts of the underlying "2" can be seen just to the upper-left of the "5" as depicted by the arrow in the example image above.
Coin Value Chart: Typical Coin Prices, Values and Worth in USD based on Grade/Condition