In 1972 the Mint issued copper nickel circulation strike coins which were struck at Philadelphia and Denver only. It also produced 40% silver Proof coins struck at San Francisco. Finally, it also struck 40% silver Uncirculated coins struck at San Francisco which carry an S mint mark but these coins weren't meant for circulation.
Instead the 40% Silver Uncirculated Eisenhower Dollars were only sold to collectors. These Uncirculated coins were sold in single packs, sometimes referred to as Blue Packs which is the nomenclature used to describe the outside packaging in which these 40% Silver Uncirculated coins were sold in.
MS60 - 63: In MS60 to MS63 they are very common since they were sold to collectors and never issued for circulation.
MS64: In MS64 they are still easily obtainable as they exist in large quantities.
MS65: In MS65 they become a little more difficult to locate mainly because they are large coins and usually some light scratches or nicks will be visible keeping them from grading any higher.
MS66: In MS66 they are still available and can be found with minimal searching. Most coins in this grade will be very nice and have great eye appeal but some light nicks, spots or scratches are just keeping it from grading any higher.
MS67: In MS67 grade they are still readily available. There are probably well over 10,000 examples that survive in this grade. Coins in this condition will have great eye appeal clean surfaces and light minimal nicks and scratches.
MS68: Coins are still somewhat easily available in this grade without much searching with many examples in this grade already being graded.
MS69: This is the ultimate grade as PCGS has graded less than two dozen from this date and mint mark in MS69 or higher. In MS69 the coin has to look almost perfect and needs to have great eye appeal with minimal spotting, nicks or scratches.