What does NDI 925 mean on a ring?

NDI 925 on a ring indicates that the metal is made of 92.5% pure silver, which is the standard for sterling silver. The "925" signifies the silver's purity, while "NDI" could refer to the manufacturer or designer's brand. This marking ensures authenticity and quality, as sterling silver is known for its durability and resistance to tarnishing compared to lower silver content alloys.