What is STER PC stamped on inside of ring mean?

The "STER" stamp on the inside of a ring indicates that the metal is made from sterling silver, which is an alloy consisting of 92.5% silver and 7.5% other metals, typically copper. This stamp signifies the quality and purity of the silver used in the piece. The "PC" may refer to the manufacturer or designer of the ring, but its specific meaning can vary depending on the context.