Yes they are all 90% silver and 10% copper. They contain .18084oz of pure silver.
Yes.
Yes. All quarters minted up through 1964 were made of 90% silver and 10% copper.
All US quarters dated 1964 or before are 90% silver.
The last year for silver quarters was 1964.
All U.S. quarters dated 1964 and earlier contain silver.
All U.S. quarters dated 1964 and earlier are silver.
Yes, all dimes, quarters, half dollars, and silver dollars 1964 and older are 90% silver.
Yes, all are 80% silver.
Yes, all are 80% silver.
All circulating quarters dated 1965 and later are made of copper-nickel, not silver.
All pre-1965 US quarters and dimes are 90% silver.
All quarters dated 1964 and before are silver, all quarters released for general circulation dated 1965-present are not silver. The US mint has released quarters struck in 40% silver for collectors during the US Bicentennial and 90% silver proof sets for collectors in 1992-present.