What this coin looks like (obverse, reverse, mint mark location, special features, etc.):
This is a D Over S (D/S) Jefferson Nickel mintmark variety. In the image depicted above: One way to determine this error is there will be a D stamped over a subtle S mint mark with the S being most noticeable on the left-hand side of the D mark.
Coin valuation chart: Typical coin prices, values and worth per grade or condition - in USD