Denver Washington Quarter
30% Straight Clip and Broadstruck
Struck on a Proof Planchet
PCGS MS 66
UNIQUE
SOLD

This is a unique discovery mint error. Somehow a specially prepared proof planchet intended for striking of proof quarters was mixed in with uncirculated blanks striking mint state coins in Denver. This type of error has only occurred on modern coinage. The Philadelphia Mint prepares the proof blanks which are then sent to San Francisco or West Point for striking. I discovered several SBA Dollars struck on specially prepared proof blanks that were also off-center or broadstruck, but struck by regular dies intended for circulating coinage.

These coins that are struck on specially prepared proof planchets have an extreme proof-like field and a pitted appearance both on the surfaces and unstruck portions. This Denver struck Washington quarter has these characteristics. This new discovery makes this the second known Denver Mint U.S. coin struck on a specially prepared proof planchet intended for proof strikes. The original discovery coin was a 1972 Denver quarter struck on a proof Nickel planchet.

There are a few known 1977 Denver Ike Dollars struck on 40% Silver-Clad planchets intended for striking the 1976-S San Francisco proofs, but these are not on specially prepared proof blanks.

In my NLG Award winning book, World's Greatest Mint Errors, Chapter 23: Proof Planchet Errors (page 169), I describe and illustrate U.S. coins struck by circulation dies but on specially prepared proof planchets. This is an extremely rare mint error.