What this coin looks like (obverse, reverse, mint mark location, special features, etc.): There are two major versions of the 1972-S Eisenhower Dollar - both of them have a silver-clad composition with a 40% silver content. The common version is the 1972 Brilliant Uncirculated silver Eisenhower Dollar (as depicted above) which came in the blue pack/envelope with a blue seal ("Blue Ikes"). These were special mint condition coins sold to collectors.
The other version is the 1972 S Silver Proof Eisenhower Dollar which came in proof sets or brown boxes with a gold eagle seal ("Brown Ikes") - only 1811631 of these mirror-like silver proof coins were produced. An example of the proof version is depicted below:
Coin value chart: Typical coin prices, values and worth in USD based on grade/condition