This is the only known proof Bicentennial Quarter struck over a Roosevelt Dime. In addition, it is a "dual date" since the dime is dated 1967, an amazing 9 years apart!
The 1976 Proof Bicentennial Quarters were struck at the San Francisco Mint. The 1967 Dimes do not have a mint mark since they were struck at several U.S. Mints. Struck as circulating coinage in 1967 at the Philadelphia and Denver Mints, and struck as special specimen coins (SMS) to be included in the Special Mint Sets in San Francisco at the Mint.
Since no Mint Mark designates which U.S. Mint struck the 1967 U.S. Dimes, the only way to determine if this 1967 Dime was struck in San Francisco would be the special surface and strike on the SMS Dimes. Since this Dime was overstruck by proof quarter dies for the 1976 Bicentennial Quarter, no determination can be made.
1976 Bicentennial off-metal mint errors are very rare in every denomination struck for circulation. In proof, they are prohibitively rare with only 3 proof Bicentennial off-metal double denominations known on any denomination. There are (2) Bicentennial proof quarters struck over struck cents known and now this just discovered and unique 1976-S Bicentennial quarter struck over a struck 1967 dime.
For comparison purposes, in a Heritage auction, a NGC Mint State 64 Bicentennial Quarter on a Dime blank sold for $6,900. Also in a Heritage auction, a Bicentennial quarter struck on a struck Dime in PCGS Mint State 62, sold for $9,200. Jon Sullivan, a coin dealer specializing in mint errors, sold the only known Bicentennial quarter struck on a dime blank in PCGS Proof 67 in the low 5 figure range.
This unique mint error offered here was just discovered and was authenticated and certified Proof 67 by NGC. It is unique and is a significant discovery for several important reasons. It is the only known Bicentennial quarter struck over a struck dime in proof. It is also a "dual date" Bicentennial 1976-S quarter overstruck on a 1967 dime, 9 years apart. It was either struck in Philadelphia or Denver for circulation or San Francisco on a specially prepared SMS planchet.
It was preserved in amazing condition with considerable detail remaining on both the obverse and reverse. The obverse design of the dime is mostly visible underneath the design of the obverse design of the quarter. The full date 1967 is clearly visible giving it a remarkable and dramatic look of the dual date 1976-S and 1967.
This discovery mint error is fascinating since it combines rarity (unique), quality (Proof 67), history (Bicentennial one year only design), intrigue (either struck in Philadelphia or Denver for circulation or in San Francisco as SMS) and mystery (9 years apart). This enigmatic and unique U.S. proof mint error belongs in a major collection of the finest error coins or in a collection of Bicentennial coins.
Below is a 1967 Roosevelt Dime image
transposed on this mint error:
Below is the unique Proof Bicentennial Quarter
struck on a dime blank that Jon Sullivan
privately sold in the low 5 figure range:
Featured on the cover of Mint Error News Magazine Issue 56:
Also for comparison, below are the two famous and enigmatic Washington Quarters from the San Francisco Mint struck in Proof, over a U.S. Silver Barber Quarter (1892-1916) and over a 1941 Canada Silver Quarter. These were both featured in a TV interview I did with Fox News. These fascinating errors went "viral" and were featured in USA Today, London's Daily Mail, AP News, Coin Week, New York Post, Newsmax, NBC News, Numismatic News, Time Magazine and on Maria Bartiromo's TV show.
Proof Errors are featured in the NLG award
winning book, World's Greatest Mint Errors.