Although I could be wrong, I believe that the coin is probably a genuine Silver Capped Bust Half Dollar minted sometime between 1807 and 1836 that just looks as if it is Copper. Remember, the Silver Half Dollar coins were 90% Silver and 10% Copper. Extreme heat from a fire or being very close to a fire can cause the Copper to rise to the surface of Silver coins. Also, the color could have been caused by environmental contaminants in the soil where the coin has been for the past say 175 to 200 years. Two things will show whether the coin is Silver or if it is Copper and that is the weight and the ring test. A normal Capped Bust Half Dollar minted from 1807 to 1836 should weigh 13.48 grams, while a normal Classic Head Large Cent minted from 1808 to 1814 should weigh 10.89 grams. Depending upong how much corrosion and encrustation is on the coin but considering there is wear on it, if it is Silver or Copper, it should not weight too significantly far from either weight. While the corrosion and encrustation on the coin may somewhat deaden the sound tone when the coin is dropped on a hard surface such as a Coffee table or Counter Top, I believe that this test and the sound tone that comes from the coin, will likely be the tell tell sign of whether it is Silver or Copper.
Frank