Unique Dual Mint Mark Discovery
Proof 1776-1976 S Bicentennial Quarter
Overstruck on Struck Lincoln Cent
Struck by both San Francisco and Denver Mints
NGC PF 67 RD
Unique Dual Mint Mark Discovery
Upon closer examination of the understrike on the reverse of the quarter, Jon Sullivan of Sullivan Numismatics discovered and successfully matched up the "D" mint mark. The copper Lincoln Cent was originally STRUCK IN DENVER prior to being overstruck by Proof Bicentennial Dies in San Francisco. To date, this is the only known proof U.S. coin that shows 2 mint marks from 2 different U.S. Mints.
The "D" mint mark is visible
between the M and E of AMERICA
This is the only known
proof U.S. coin that shows two mint marks
from two different U.S. Mints. It is a double denomination
Bicentennial Quarter struck over
a struck Lincoln Cent. There is one other proof Bicentennial Quarter double denomination known, which is struck over a 1969-S Lincoln Cent.
The 1976 Proof Bicentennial Quarters were struck at the San Francisco Mint. Somehow a Lincoln Cent that was struck in Denver was subsequently struck by proof Bicentennial Quarter dies at the San Francisco Mint.
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 is a unique 1976-S Bicentennial Quarter struck over a struck 1967 Dime, the 1976-S Bicentennial proof Quarter struck over a 1969-S Lincoln Cent mentioned above and this just discovered unique dual mint mark proof Bicentennial Quarter struck in San Francisco over a Denver minted Cent.
Proof coins are struck by technicians who hand feed the blanks into special presses. They are produced, examined and packaged using extreme quality control. It is very unusual to find major proof errors. A few broadstrikes, off-centers, double strikes (in collar) and off-metals have been known to be found in sealed proof sets. Proof errors are aggressively sought after by many error collectors.
A very small group of Proof errors recently came from a collection that was auctioned by the State of California. The U.S. Secret Service inspected and released this collection to the State of California determining that it was legal to own. The State of California then auctioned the collection and it has been dispersed since the sale.
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 proof Bicentennial Quarter double denomination with two different mint marks. It was preserved in amazing condition with considerable detail remaining on both the obverse and reverse. The reverse design of the Cent is mostly visible underneath the obverse design of the Quarter. The obverse design of the Cent is mostly visible underneath the reverse design of the Quarter, with the "D" mint mark visible between the M
This discovery mint error is fascinating since it combines rarity (unique), quality (Proof 67), history (Bicentennial one year only design) and intrigue (the only known proof U.S. coin that shows mint marks from two different U.S. Mints). 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.
Also just discovered 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! This unique double denomination was certified by NGC.
Proof errors are featured in my NLG Award winning book, World's Greatest Mint Errors.