This is a question I am often asked so here is a brief description of the series.
The Eisenhower dollar was the last full size dollar minted by the US mint for circulation. Even though they were only made for 8 years the mint managed to make quite a variety of them. All of the silver Ikes were made of 40% silver.
The series started in 1971 and there were 4 different coins made. 1971 P and D in copper-nickel clad and the 1971 S BU sliver commonly known as the Blue Ike for the color of the package they were issued in and 1971 S silver proof or Brown Ike for the brown box they came in.
The same 4 coins were made in 1972 for another 4 Ikes.
In 1973 the mint added an S mint copper clad proof to give this year 5 Ikes.
Then again in 1974 there were the same 5 Ikes made.
In 1975 the mint was getting ready for the bicentennial year and went ahead and made Ikes but put the year 1776-1976 on them so there are no 1975 dated dollar coins. In 1976 they changed the reverse dies for the P and D mint coins so there are type 1 with wide letters on the reverse (minted in 1975) and type 2 with narrower lettering. There is also the 1976 silver BU and 3 proof coins, 1976 S type 1 and 1976 S type 2 copper clad proofs and 1976 S 40% silver clad proof. So that gives us 8 different coins with 1776-1976 on them as follows:
1976 type 1 with the wide lettering on the reverse, 1976 type 2 1976 d type 1, 1976 d type 2, 1976 s proof type 1, 1976 s proof type 2, 1976 s silver BU and the 1976 s silver proof
For 1977 and 1978 there are only 3 coins of each year. 1977, 1977 D and the 1977 S copper-clad proof and 1978, 1978 D, 1978 S copper-clad proof for a total of 6 for these 2 years as no silver coin were made.
Now, that seems to give a grand total of 32 Eisenhower dollars for the 8 years of production and if you have an album that is what you will see. There are also, in 1972 three varieties of the Philadelphia minted coin that may be of interest. The way to identify these varieties it to look at the small world symbol on the reverse of the coin. The type 1 has the islands under Florida below and to the right and is by far the most common. The rarest one is the type 2 and there the islands kind of indistinct and vague (this is the same as on the 1971 s silver proof). The type 3 has well defined islands and the biggest one is centered under Florida or even a bit to the left. With these 3 varieties that brings the total up to 34 coins, quite a group for just 8 years of production.
I hope you found this information useful.