What this coin looks like (obverse, reverse, mint mark location, special features, etc.): There were multiple varieties of the 1907 $10 Gold Indian Head Eagle - some extremely rare and valuable. One major variety is the "Round Rim" - also known as the "Rolled Rim" type without the extra Periods on the reverse of the coin. This variety is common - unlike the ultra-rare variety with the extra periods.
The "Wire Rim" design was actually the original design created by Augustus Saint Gaudens - which did not include a rim on the coin. The coin making process created a "fin" of excess gold that could easily be broken off and devalue the coin - making it troublesome for trade. The lack of rim also caused the date and design to be worn down prematurely. Eventually Chief Engraver Charles Barber included a rim to the die in order to solve the problem. About 500 of these coins were produced and distributed to government officials. Barber's Rounded Rim (or Rolled Rim) design is easily distinguishable with the addition of the rim on the coin. The difference between the Wire Rim vs Rolled Rim is depicted below in the example comparison image (Source of example images is courtesy of Heritage Auction Galleries):
There were two major sub-varieties of the Rounded Rim variety. One variety features periods around each of the words in the legend: *E* *PLURIBUS* *UNUM* and also: *TEN*DOLLARS* on the reverse of the coin. This is the extremely rare and valuable variety. The common "No Periods" variety was produced later on and has no periods before and after "TEN DOLLARS" (except between: TEN * DOLLARS). The difference between the "With Periods" vs "No Periods" is depicted below in the example comparison images (Source of example images is courtesy of Heritage Auction Galleries):
Coin value chart: Typical coin prices, values and worth in USD based on grade/condition