What this coin looks like (obverse, reverse, mint mark location, special features, etc.): One major variety of the 1971-D Eisenhower Dollar is the Type 1 "Friendly Eagle" variety (FEV) - which is sometimes known as Variety 1 or RDV-006. This variety is less common and only between 500000 and 1000000 are estimated to exist although the exact amount is unknown.
It is fairly easy to identify this coin as there are three features on the reverse to look at. This coin got the "Friendly Eagle" name due a change in the eagle portrait. The common reverse (type 2) features an eagle with a browline above the eye. Although "Friendly Eagle" (type 1) is missing this browline above the eye - giving the eagle a less foreboding and more friendly appearance. The difference between the friendly eagle vs common eagle is depicted below in the example comparison image:
Another feature to look at is the portrait of the planet earth in the background of the coin. This is actually one of the easiest ways to identify the 1971-D type 1 vs type 2 varieties of this coin. Both varieties depict United States mainland and the Caribbean islands. The Gulf of Mexico is not as round and has a different shape in the type 2 reverse - While the friendly eagle reverse (type 1) features a rounder and more open Gulf of Mexico.
The type 2 common reverse looks like it has only 3 blobs for islands with two of them lined up - whereas the type 1 reverse looks like it has 6-7 islands lined up in a chain with one slightly below the chain.
The US East Coast goes up in nearly a straight line on the type 1 common reverse - but the East Coast on the type 2 variety appears to have a bump that extends outwards. Also the West Coast in the type 1 friendly eagle design is struck in noticeably higher relief and is "taller" or sticks outwards more (as is much of America in this design) than the type 2 variety.
Lastly: The State of Florida is oriented and points more towards the south in the type 1 friendly eagle variety - and points more towards the south-east in the common reverse. The difference between the type 1 earth vs type 2 earth is depicted below in the example comparison image:
The last major feature to look at is the crater located between the letters "L" and "A" in the word "DOLLAR". The Type 1 Friendly Eagle variety features a much more detailed crater and has been modified with accented crater lines (the other craters also have slightly more detail as well). There are more debris lines extending downward from the crater rim. The smaller crater located just to the upper-right of this crater has a large rock located in the middle of the base of the crater. The type 2 common reverse does not have these detailed features around the craters. The difference between the 1971-D Type 1 vs Type 2 Craters are depicted below in the example comparison image:
Coin valuation chart: Typical coin prices, values and worth per grade or condition - in USD