Philadelphia. With the exception of nickels dated 1942-1945, coins minted in Philadelphia didn't have a mint mark until 1979 for dollars and 1980 for halves, quarters, dimes, and nickels.
It's a common date, still worth one dollar in circulated condition.
The mint mark of the Denver Mint (shown as a "D") and the San Francisco Mint (shown as "S) on the Eisenhower Dollar is located on the obverse (heads) side of the coin directly beneath the bust of Eisenhower. If there is no mint mark there, then the coin was struck at the Philadelphia Mint and in this mint did not place a mint mark on the coins struck there until 1979.
The mint mark on Eisenhower dollars is on the front, below Ike's neck and above the 7 in the date.
San Francisco
The 1971 Eisenhower proof dollar is valued from about $10 to $65 depending upon the quality of the coin.
An uncirculated Philadelphia half from 1972 retails for about $1.
No mintmark just means it was made in Philadelphia, and adds nothing to the value of this one dollar coin.
The mint mark on Eisenhower dollars is on the front just below Ike's neck.
The mint mark position on all Eisenhower dollars is the same, above the date.None = PhiladelphiaD = DenverS = San Francisco (proof coins only)
The S above the date is the mint mark for the San Francisco mint and identifies it as a proof coin for the Eisenhower seires of dollar coins.
It's actually made of copper-nickel, not silver. The mint mark position is the same on all Eisenhower dollars, between the date and the bottom of Ike's image. No mint mark = Philadelphia D = Denver S = San Francisco (collectors' versions only)
Unless the Eisenhower dollar came from a special mint set, it is only worth $1. If you have an "S" mint mark though, it may have come from a mint set and worth significantly more.