What this coin looks like (obverse, reverse, mint mark location, special features, etc.): One major variety is the 1961 Franklin Silver Half Dollar Doubled Die Reverse (DDR) Proof. This error variety features a very prominent doubled die of the entire reverse or back of the coin - and only appears on proof coins. It is very easy to spot this variety as the doubling of the lettering is most noticeable on the left and bottom portion of the coin. The words "E PLURIBUS UNUM" and "HALF DOLLAR" and "UNITED" are where the doubling is strongest. 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