U.S. 1970-S Proof Washington Quarter
Overstruck on a Canadian Quarter
King George V (1911-1936)



This unique 1970-S Proof Quarter from the United States was overstruck on a Canadian Quarter that circulated during the reign of King George V from 1911-1936. It was authenticated and certified by NGC as PR64. This was from a group of San Francisco Proof Errors that was auctioned by the State of California. There is a significant amount of detail on both sides showing the design of the Canadian Quarter. This is a flip-over where the obverse design of the Canadian Quarter which shows the portrait of King George V is visible underneath the U.S. Quarter reverse design. The reverse design of the Canadian Quarter showing the wreath is visible underneath the U.S. Quarter obverse design. This is one of the most fascinating and intriguing proof mint errors ever discovered.

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 different 1970-S Proof Quarter from the United States was overstruck on a 1941 Quarter from Canada. It was authenticated and certified by NGC as PR65. The unique 1970-S Proof Washington Quarter overstruck on a 1941 Canadian Quarter is the only one known with King George VI. It went viral and was featured on Fox News, USA Today and countless other publications.




These 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.


Featured on USA Today! Click For Article & Video...

Featured on the cover of Mint Error News Magazine Issue 37



Featured in an article on Numismatic News

Numismatic News


Intentional Errors

One of the most controversial categories of U.S. coins are mint errors. Many dealers and collectors, as well as coin auction houses, buy, sell, trade and auction many rare, exotic and unique major mint errors. Obviously, some of these defy logic and were intentionally created and taken out of the Mint.

In the early 2000's, a group of several hundred U.S. error coins were found in a safe-deposit box. Fred Weinberg purchased this group which included coins struck for proof sets and also coins struck for circulation. This group was auctioned by the California State Controller's Office of Unclaimed Property. 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 the rest is history.

Another example of U.S. error coins escaping the Mint occurred in the 1970's. A hoard of proof error coins were smuggled out of the San Francisco Mint inside the oil pans of forklifts that were being serviced outside of the Mint. This topic was discussed in the June 6, 2022 Issue of Coin World, which covered Fred Weinberg's account of this story. The Coin World Managing Editor concluded:
Obviously, the marketplace accepts these coins, and some collectors are happy paying thousands of dollars for coins that show every indication of having been created through illegal means.

In Episode 11 of the PCGS video series Slab Lab, Seth Chandler interviews Fred Weinberg. In part 2 of the interview, Fred explains in detail why mint errors that are decades old are not recovered by the U.S. Mint. Fred's recollection of conversations in his office with the Chief of the U.S. Mint Police are extremely insightful and explain why the Mint doesn't attempt to recover error coins from decades ago.

Proof Errors are featured in Chapter 21 of my
NLG award winning book, World's Greatest Mint Errors:



The Mint Error News website has a 69 page report of coins struck by the U.S. Mint for foreign countries. It is the most comprehensive report available anywhere. Click here for a pdf of the 69 page report.

Foreigners In The Mint

Click here for a pdf of the 69 page report.