Ray writes: I read in a coin book that a Lincoln cent “1990 proof…without the S” is a somewhat rare coin. Is this true? What does 1990 proof…without the S mean, does it mean an ordinary 1990 Lincoln cent without the letter “D” or “S” under the date? Any info would be appreciated. Thank you for your time.
Proof coins are specially made coins struck with specially prepared dies and blanks. The coins are struck twice or more and are carefully handled one at a time. They exhibit mirror fields and often, frosted devices (the design elements). Proof coins are not designed to be spent, though they could be as the designs are identical to their standard circulating cousins though in higher relief.
Proof coins are sold to collectors in sets of proof examples of all the circulating coins of that year. Currently, only proofs are struck at the San Francisco Mint. In prior years the mint mark was added with a punch that was supplied by the Philadelphia Mint and the mint mark was stamped into each die individually. (Mint marks are now part of the finished die).
In 1990 a proof die failed to receive the “S” mint punch and proof coins struck with that die are missing the mint mark. Examples of this error currently bring approximately $1,000. For further reading, see the article Observations on Proof Coinage.