Specially minted
coin, that receives multiple blows from polished
dies in order to make details of the
coins sharper. Current US Proofs have frosted devices and polished fields. Before the ‘70s only the first few coins from each die had frosted devices, as a result early
cameo proofs command a
premium. Because the coins are not annealed between strikes the dies wear out quickly.
Die Life Reported by U.S. Mint 1971
Penny
Business Strike - 1,000,000 Obv / 1,200,000 Rev.
Proof - 2,300 Obv /2,900 Rev
Nickel
Business Strike - 170,000 Obv / 185,000 Rev.
Proof - 2,500 Obv / 2,300 Rev
Dimes
Business Strike – 150,000 Obv / 165,000 Rev
Proof – 2,600 Obv / 2,500 Rev
Quarters
Business Strike – 155,000 Obv / 170,00 Rev
Proof – 1,500 * Obv / 2,200 Rev
Halves
Business Strike – 150,000 Obv / 180,000 Rev
Proof – 2,400 Obv / 3,200 Rev
*
Walter Breen – believed this to be an error with the true amount being 2,500
Source: Numisatic Scrapbook Magazine 9/72 pp. 842-43