What this coin looks like (obverse, reverse, mint mark location, special features, etc.):
This is a 1883 3/2 Overdate Shield Nickel error. The 1883 date was stamped on top of the 1882 date which resulted in a 3 being stamped over a subtle 2. The 2 is still legible and is 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