What This Coin Looks Like (Obverse, Reverse, Mint Mark Location, Special Features, etc.): There were two major varieties of the 1861-S Liberty Head $20 Gold Double Eagle. The common variety features the normal design on the reverse of the coin (as depicted above) - while the other rarer variety is known as the "Paquet Reverse" variety. The difference between the Normal Reverse vs Paquet Reverse is depicted below in the example comparison image. Note the styling and size differences in the letters along with the "S" mint mark - and also the rays within the circle of stars above the eagle (Source of example image is courtesy of Heritage Auction Galleries):
Coin Value Chart: Typical Coin Prices, Values and Worth in USD based on Grade/Condition