The 1978 S United States Proof Washington Quarter is a 25 cent coin made of clad composition, with a fineness of 0.75. Minted in San Francisco, this coin features a proof strike type and is part of the Washington variety, showcasing the iconic image of President George Washington. As a piece of American currency from 1978, this uncirculated coin is a valuable addition to any coin collection, representing a significant moment in US coinage history.