What this coin looks like (obverse, reverse, mint mark location, special features, etc.):
The 1937 D 3 Legs Buffalo Nickel error can be identified by looking at the legs of the buffalo on the reverse of the Indian head nickel. There will be 3 solid legs but the front leg will be clearly missing. Hence it will look like 3 legged buffalo as depicted in the example image of the coin above.
Coin valuation chart: Typical coin prices, values and worth per grade or condition - in USD