Stack's Bowers Galleries is pleased to present the newly confirmed and unique 1966 Washington quarter struck on a 90% silver planchet. It is a transitional wrong planchet error produced at a time when the United States Mint was discontinuing circulation strike quarter (and dime) production in an alloy of 90% silver, 10% copper and replacing it with the now-familiar copper-nickel clad coinage. The most famous wrong planchet errors attributed to the United States Mint are the 1943-dated Lincoln cents struck on bronze planchets and their close cousins, the 1944-dated cents struck on zinc-coated steel planchets. As those two coins suggest, most transitional wrong planchet errors were struck the year in which the Mint began using planchets of a different metallic composition. The generally accepted theory for the creation of these errors is that a small quantity of planchets from the previous year's coinage somehow got caught up in the folds of the delivery carts for blank planchets and/or got stuck in other Mint machinery, and in the course of the following year's coinage the stray planchets from the previous year worked their way loose and wound up feeding through the presses along with the new planchets. Indeed, the vast majority of transitional wrong planchet Washington quarter errors that resulted from the changeover to copper-nickel clad coinage are dated 1965. Writing in his 2009 reference World's Greatest Mint Errors, Mike Byers accounts for 20 examples of the 1965 quarter struck on a 90% silver planchet - an estimate that should probably be revised upward given that we have offered seven different examples since 2011, with Heritage bringing approximately a dozen to auction between 1993 and 2023.

The 1966 offered here, however, is in an entirely different category with regard to rarity and significance. Part of an effort to combat an alleged coin shortage that it did not understand, Congress authorized the Mint to continue production from 1964-dated dies until stocks of newly minted coins were sufficient to meet the needs of coin collectors and satisfy hoarders - two of the groups that the Treasury Department blamed for the shortage. Bullion prices had indeed risen to the point where hoarding of silver became profitable, which prompted the federal government to also replace the 90% silver, 10% copper composition of the quarter (and dime) with a newly adopted copper-nickel clad composition once coinage from 1964-dated dies ceased. For the quarter this happened in late August 1965, with copper-nickel clad coinage from 1965-dated dies commencing on August 23 at the Philadelphia Mint; the first copper-nickel clad 1965 quarters were released into circulation in November of that year. In an effort to discourage coin collectors, the first three copper-nickel clad issues of 1965 through 1967 were made without mintmarks even though circulation strike quarters of these dates were produced at both the Philadelphia and Denver facilities; the Special Mint Set (SMS) coins of these dates were struck at San Francisco, also without mintmark.

Given that both 1964-dated quarters on 90% silver planchets and 1965-dated examples on copper-nickel clad blanks were struck at the Philadelphia and Denver mints during calendar year 1965, it easy to account for the 1965 quarters struck on 90% silver planchets in error. The San Francisco Mint even struck 4,640,865 silver quarters from 1964-dated dies early in 1966. By the time the circulation strike quarter production from 1966-dated dies commenced on August 1, 1966, however, one would think that any and all 90% silver planchets that had remained lodged in Mint equipment after the transition to copper-nickel clad coinage had already found their way into presses fitted with 1965-dated dies or been discovered and removed by Mint employees. In October 2017, however, the numismatic community became aware of a Proof 1968-S quarter struck on a 90% silver planchet. In a press release that also announced the certification of a two-tailed quarter likely struck between 1965 and 1967, PCGS stated:

The second piece is a 1968-S Proof Quarter, struck on a 90% silver planchet (Type 2, with upset rims) left over from 1964. While a few 1965 Silver Quarters are known (and a 1966 is rumored), it is the only known post-1964 Proof Silver Quarter.

The existence of a 1966 quarter struck on a 90% silver planchet, as alluded to in this press release, remained a rumor for nearly another decade, during which time the potential to discover one of these errors continued to motivate numismatic treasure hunters. Then in 2025, while searching through quantities of 90% silver Washington quarters looking for scarce hub types of the 1964-dated issues, our consignor made the startling discovery of the coin being offered here. He submitted it to PCGS, who authenticated it as a genuine circulation strike 1966 Washington quarter struck on a 90% silver planchet. It remains unique for a 1966-dated transitional wrong planchet error (a statement that includes the 1966 silver Roosevelt dime, the existence of which is unconfirmed), and is making its first appearance in the numismatic market through Stack's Bowers Galleries' June 2026 Showcase Auction.

Overall light wear and wispy handling marks confirm that this coin evaded the Mint's quality control procedures, was released into commerce through normal channels, and circulated for a brief period of time. Its status as a Mint error was not recognized at the time it was set aside with other 90% silver quarters pulled from circulation during the early and mid 1960s. The coin retains enough detail and appreciable mint luster to support the About Uncirculated grade assigned by PCGS. Both sides are lightly toned in pale sandy-silver iridescence, the reverse periphery also with subtle lilac highlights discernible as the coin rotates under strong lighting.

One of the most significant transitional wrong planchet Mint errors we have ever offered, and rarer than the famous 1943 bronze and 1944 zinc-coated steel cents, this 90% silver 1966 quarter will serve as a centerpiece in the finest specialized collection of 20th century United States Mint error coinage.

Accepted Forms of Payment:

ACH, American Express, Discover, MasterCard, Money Order / Cashiers Check, Personal Check, Visa, Wire Transfer

Shipping

All winning lots will be shipped domestically via FEDEX, United States Postal Service, or DHL. Please note: A delivery confirmation shipment will be required for all orders. Delivery methods depend on the value of the shipment (for insurance purposes). All orders sent via Priority or Express require a signature confirmation. Please refer to the chart below to see how your winning lots will be shipped. Once your order has shipped, we will send you an email containing the order tracking information.

Total Value of Shipment Shipping Method
$1-$299 First Class
$300-$24,999 Priority or 2-Day
$25,000-$199,999 Express or Overnight
$200,000+ Contact us for Special Arrangements
Chart applies to U.S. addresses only -- items shipped to international addresses from the United States will be delivered via Fed Ex and items shipped from our Hong Office will be delivered via EMS with the exception of countries that EMS service does not cover.

If you would like your order shipped domestically via FedEx, please contact our Client Services department at (800) 458-4646. Additional charges may apply.

• How much do you charge for shipping and handling?

Within the United States: All orders are shipped via USPS. All orders will have the following postage and insurance charges in addition to a $.50 handling charge per lot added to the purchase price:

Invoice Amount Postage & Insurance
Up to $299 $12.00
$300- $499 $17.00
$500- $999 $20.00
$1000- $2499 $24.00
$2500- $4999 $27.00
$5000- $9999 $30.00
$10000- $14999 $40.00
$15000- $19999 $45.00
$20000- $24999 $50.00
$25000- $49999 $75.00
$50000- $74999 $100.00
$75000- $99999 $125.00
$100000- $249999 $250.00
$250000+ $400.00


All international orders (including Canada and Mexico) shipped from the United States will be shipped via Fedex or UPS depending on the destination country. All orders will have an international insurance fee of 1/2% of the subtotal of the invoice (hammer price plus buyers fee), with a minimum insurance fee of $10 plus a $.50 handling charge per lot in addition to the postage below. For shipments from our Hong Kong office via EMS, please refer to the Hong Kong Auction section.

Invoice Amount Postage
Up to $2,500 $50.00
$2,501-$10,000 $60.00
$10,001-$100,000 $75.00
$100,001-$200,000 $125.00
$200,001+ $500 or Contact us for Special Arrangements


All orders shipped from the Hong Kong, China Office are shipped via EMS with the exception of countries that EMS service does not cover. All orders will have an international insurance fee of 1/2% of the subtotal of the invoice (hammer price plus buyers fee), with a minimum insurance fee of $10 plus a $.50 handling charge per lot in addition to the postage below. The following countries have EMS coverage: Australia, China, Hong Kong, Japan, Laos, Macau, Malaysia, Mongolia, Singapore, South Korea, Sri Lanka, Taiwan, and Thailand. Our international shipping rates will apply to countries not covered by EMS. If you have special shipping requests from our Hong Kong, China Office, please contact [email protected].

Invoice Amount Postage
Up to $300 $35.00
$301-$1,000 $40.00
$1,001-$2,000 $45.00
$2,001-$3,000 $50.00
$3,001-$5,000 $55.00
$5,001-$10,000 $60.00
$10,001-$25,000 $70.00
$25,001-$50,000 $80.00
$50,001-$75,000 $90.00
$75,001-$100,000 $100.00
$100,000-$200,000 $125.00
$200,000+ $500.00 or Contact us for Special Arrangements

by Stack's Bowers Galleries
June 16, 2026 12:00 PM PDT
1550 Scenic Ave
Suite 150
Costa Mesa, CA, US 92626

Stack's Bowers Galleries

You agree to pay a buyer's premium of 27% and any applicable taxes and shipping.

View full terms and conditions

Bid Increments
From: To: Increments:
$0 $99 $20
$100 $199 $20
$200 $499 $20
$500 $999 $50
$1,000 $1,999 $100
$2,000 $4,999 $200
$5,000 $9,999 $500
$10,000 $19,999 $1,000
$20,000 $49,999 $2,000
$50,000 $99,999 $5,000
$100,000 $199,999 $10,000
$200,000 $499,999 $20,000
$500,000 $999,999 $50,000
$1,000,000 $1,999,999 $50,000
$2,000,000 + $100,000