What this coin looks like (obverse, reverse, mint mark location, special features, etc.):
One major variety is the 1823/2 overdate error of the Coronet Head Large Cent (Penny). This coin features an 1823 date struck on top of an 1822 date which resulted in part of the underlying "2" being visible within and around the "3". These features are depicted in the example image of the coin above.
Coin valuation chart: Typical coin prices, values and worth per grade or condition - in USD