The United States began minting silver dimes and quarters in the year 1796.
Basically, 90% Silver, 10% Copper, for United States.
The United States did not produce quarters from silver in 1970, only ones from an alloy of copper and nickel.
U.S. quarters dated 1964 or earlier are 90% silver and 10% copper, they contain .18084oz of pure silver.
The composition of quarters in the United States changed in 1965. Prior to that, quarters were made of 90% silver. However, starting in 1965, the composition of quarters changed to a mix of copper and nickel, which is still used today.
1964 was the last year US quarters were made of Silver.
1964 was the last for quarters and dimes
64 was last year on dimes quarters, etc. Compare a 64 & 65. You will see a copper band on ridged side of 65's & later.
Quarters minted before 1964 in the United States were made with 90% silver and 10% copper.
The last year for circulating silver U.S. quarters (and dimes) was 1964. Half dollars contained silver until 1970, but at a reduced amount.1964 was the last year silver quarters were issued for general circulation.
For general circulation, 1964.
US quarters dated 1964 and before weigh 6 25 grams. and are 90% silver 10% copper.
The approximate value of 50 uncirculated 1964 United States Quarters would depend on the current market value of silver, but is likely to be between $75 and $150.