What this coin looks like (obverse, reverse, mint mark location, special features, etc.): One major variety is the 1972 Type 3 Eisenhower "Ike" Dollar - also known as Variety 3. The varieties of this year largely deal with the styling of the depiction of earth on the reverse of the coin and the differences are very subtle - but easy to distinguish.
The Type 1 dollar features three islands off the coast of Florida - All of them are east of the eastern edge of the Gulf of Mexico (or western edge of Florida). This variety is of lower relief and was used in most copper-clad and uncirculated silver dollars of 1971 and most copper-clad 1972 dollars.
The Type 2 dollar features a higher relief and rounder earth - but the islands are very indistinct. Usually the islands appear to lump into one very large island or indentation where the islands would normally appear on the coin. This variety was used in most proof dollar coins of 1971 and all silver dollars of 1972. This variety is also found on a very few copper-clad Ike dollars in 1972 - and this is an extremely rare and valuable variety!
The last major variety is the Type 3 Eisenhower dollar which also features a high relief strike. Except this variety has 3 very clearly visible islands like the type 1 variety. The difference is that the upper-left island extends in towards the Gulf of Mexico - far past the western edge of Florida. The bottom-left island is also larger and is oriented more towards the west. This design type was used for later 1972 dollars and in the years afterwards.
The difference between the 1972 Type 1 vs Type 2 vs Type 3 Eisenhower Dollar varieties is depicted below in the example comparison image:
Coin valuation chart: Typical coin prices, values and worth per grade or condition - in USD