What this coin looks like (obverse, reverse, mint mark location, special features, etc.): One major variety is the 1950 D/S Washington Quarter. This coin features a Denver "D" mintmark struck and punched over a San Francisco "S" mint mark (OMM variety). The best way to identify this coin is to note that parts of the underlying "S" are seen near the upper/upper-left portion of the "D". The "D" appears slightly doubled just to the right of the "D" mintmark. These features are depicted by the arrows in the example image above.
Coin value chart: Typical coin prices, values and worth in USD based on grade/condition