What this coin looks like (obverse, reverse, mint mark location, special features, etc.): There were two major varieties of the 1917 S Walking Liberty Half Dollar. The earlier and rarer variety had the "S" mint mark on the obverse of the coin with a location under the words "IN GOD WE TRUST". Later on the "S" mint mark was moved to the reverse of the coin with the location just to the left of the rock that the eagle is perched on and just below the branch. The variety depicted above features the mint mark on the reverse of the coin.
Coin valuation chart: Typical coin prices, values and worth per grade or condition - in USD