What this coin looks like (obverse, reverse, mint mark location, special features, etc.):
There were two major varieties of the 1907 High Relief $20 Saint Gaudens Gold Double Eagle. One variety features a "Wire Rim" (as depicted above) while the other featured a "Flat Rim". All High Relief coins feature the MCMVII Roman Numeral date.
The Wire Rim variety features a very thin and raised rim at the very outer rim of the coin - whereas the Flat Rim variety does not have this thin raised wire rim. In order for a coin to qualify as "Wire Rim" - the raised wire rim needs to be present through the entire circumference of the coin. The difference between the Wire Rim vs Flat Rim is depicted below in the example comparison image (Source of example images is courtesy of Heritage Auction Galleries):
Coin valuation chart: Typical coin prices, values and worth per grade or condition - in USD