What does 575 mean on a necklace?

The number "575" on a necklace typically refers to the purity of the metal, specifically silver. In this context, it indicates that the piece is made of 57.5% silver, meaning it is likely sterling silver, which is commonly composed of 92.5% silver and 7.5% other metals. However, "575" can also appear on items made from other materials, so it's always good to check the context and the specific metal composition.