What is sterling silver that is marked 555?

Sterling silver is an alloy composed of 92.5% silver and 7.5% other metals, typically copper, to enhance its strength and durability. The marking "555" indicates that the item is made of 55.5% silver, which is not considered sterling silver. Instead, this marking suggests a lower silver content, often associated with a type of silver known as "coin silver," which can vary in silver purity.