What does 925 dm mean on a ring that's old?

The marking "925" on an old ring indicates that the piece is made of sterling silver, which is composed of 92.5% silver and 7.5% other metals, typically copper. This standard is commonly used for silver jewelry to ensure durability while maintaining the precious metal's value. The "dm" could refer to the maker's mark or a specific design or style, but without additional context, its exact meaning is unclear. Overall, the 925 mark signifies quality and authenticity in silver jewelry.