The Bicentennial dollars were the first of the three denominations to be struck for distribution to the public; these were coined beginning in February 1975. The silver pieces were struck at San Francisco beginning on April 23, 1975. The Mint found that the copper nickel dollar was striking indistinctly, a problem not seen with the silver pieces. Brooks called a halt in production to allow Gasparro to modify the dies; the most noticeable change is that the revised issue, or Type II as it came to be known, have narrower, sharper lettering on the reverse. All silver pieces (struck only at San Francisco) are Type I; all three mints struck both Type I and Type II copper nickel pieces. All dollars included in 1975 proof sets are Type I; all those included in 1976 proof sets are Type II. The first Bicentennial dollars were released into circulation on October 13, 1975. Over 220 million were struck. The Bicentennial design was not used after 1976; sets of silver clad Bicentennial coins were sold by the Mint until sales were finally closed at the end of 1986.