
Based on the provided information, the key year regarding silver content in common United States coinage is 1964. Dimes, quarters, half dollars, and silver dollars minted in 1964 and in preceding years are recognized as containing silver.
This date serves as a critical dividing line for identifying circulating coins with high silver content. The provided context specifically refers to these coins dated "1964 & older" as "junk silver," a term used to describe silver coins whose value is primarily derived from their silver bullion content rather than their numismatic or collectible rarity. Therefore, for general U.S. circulation coins, 1964 was the final year of production for 90% silver composition.


