which quarters are 40 silver

[McBrooklyn]

Based on the provided information, the only United States quarter ever issued with a 40% silver composition is the Bicentennial Washington Quarter minted in 1976. These coins were created to commemorate the 200th anniversary of the United States and feature a special reverse design of a colonial drummer.

An essential distinction is that these 40% silver quarters were not produced for general circulation. They were exclusively available as part of special collector sets issued by the U.S. Mint, specifically the three-coin proof and uncirculated sets that also included the 40% silver Bicentennial half dollar and dollar. The composition of these numismatic coins consists of outer layers containing 80% silver and 20% copper bonded to an inner core of 20.9% silver and 79.1% copper, which results in the overall 40% silver content. Consequently, any Bicentennial quarter found in circulation would be a standard copper-nickel clad version, not the silver variety.