United States quarters, initially composed of 90% silver and 10% copper, underwent a change in their metallic composition during the mid-20th century. These coins, once a valuable source of silver, transitioned to a clad composition due to economic pressures. Consider a pre-1965 quarter; its intrinsic value was largely determined by its silver content.
The shift away from silver was primarily driven by rising silver prices. As the value of silver increased, the face value of the quarter became less than the value of the silver it contained. This created a situation where it was economically advantageous to melt down quarters for their silver content. This practice threatened to deplete the coinage supply and destabilize the economy.