In 1973, the United States Mint began packaging copper-nickel versions of the coin in standard annual proof sets, though continued offering 40% silver proofs on an individual basis.
While all regular-issue Eisenhower dollars were made with copper-nickel clad, in 19, all proofs were struck as 40% silver numismatic specimens that were sold individually in brown-colored boxes. Proof Eisenhower dollars were minted from 1971 through 1978, which is the duration of the series.
