1990 No S Proof Lincoln Cent PR69RD DCAM PCGS Famous Error Coin! In 1990 the San Francisco Mint apparently omitted the S mintmark punch for a small number of proof Lincoln cents, all of which should normally show an S mintmark. This 1990 No S proof is certified PR69RD Deep Cameo by PCGS, one of fewer than five dozen “grading events” at this top level (and a number that, like all such estimates, surely contains numerous duplications). Even though the closeup of the obverse appears to show some squiggly lines between Lincoln’s bowtie and the 1 of the date, it is merely a reflection—both sides of this coin are as smooth as a baby’s butt. An in-demand variety in the top grade at PCGS, which has never certified a PR70 example.