What does the stamp Du stand for on a ring?

The stamp "Du" on a ring typically indicates that the piece is made of "Duplex" or "Du" gold, which is a type of gold alloy. This designation is often used to signify a specific gold content or quality level. However, it can also refer to a specific manufacturer or jewelry brand, depending on the context. Always check with a jeweler for the exact meaning in relation to a specific item.