* 925: This signifies that the metal is Sterling Silver. Sterling Silver is an alloy made up of 92.5% pure silver and 7.5% of another metal, usually copper.
* DM: The "DM" is likely a maker's mark or brand identifier. It represents the initials or logo of the jewelry manufacturer or designer.
So, putting it together, "DM 925" means the item is made of Sterling Silver and was made by a company or artisan whose mark is "DM".