What this coin looks like (obverse, reverse, mint mark location, special features, etc.):
One major variety is the 1847/7 Braided Hair Large Cent (Penny) Overdate Error. This features a large 1847 date struck over a small 1847 date. This variety can be identified by noticing a portion of the underlying smaller "7" just above the larger "7". In some cases a portion of the smaller underlying "4" can be seen just above the larger "4". These features are depicted by the arrows in the example image of the coin above.
Coin valuation chart: Typical coin prices, values and worth per grade or condition - in USD