Most 1972 Eisenhower dollars were struck with a copper-nickel clad metallic base, as most large-denomination U.S. coins were beginning in 1971. However, with approval from the U.S. Treasury, the United States Mint struck around 4 million Eisenhower dollars with a 40 percent silver metal content. These silver Eisenhower dollars were all made at the San Francisco mint and were offered in both proof and uncirculated varieties.