What does ster mean stamped ona silver locket?

The term "ster" stamped on a silver locket typically stands for "sterling," indicating that the piece is made of sterling silver, which is composed of 92.5% silver and 7.5% other metals, usually copper. This mark signifies the locket's quality and authenticity as a precious metal item. It's common to see such markings on jewelry to assure buyers of the material's value.