What this coin looks like (obverse, reverse, mint mark location, special features, etc.):
The 1917 Doubled Die Obverse DDO Lincoln Wheat Cent (Penny) is one of the more valuable doubled die errors. This can best be identified by noticing the doubling of the words "IN GOD WE TRUST" and the 1917 doubled date as depicted in the example image above. Example Image Courtesy of Heritage Auctions.
Coin valuation chart: Typical coin prices, values and worth per grade or condition - in USD