What is a diamond cross pendant stamped with an n circled and 923?

A diamond cross pendant stamped with an "N" circled and "923" typically indicates that it is made from 92.3% pure silver, which is commonly referred to as sterling silver. The "N" may represent a specific manufacturer's mark or the designer's logo. The presence of diamonds suggests that the pendant is both decorative and valuable. It's advisable to have such pieces authenticated by a professional jeweler for accurate identification and appraisal.