925 sterling means that the metal is 92.5% pure silver. The rest is copper and other alloys. The alloys are added to the silver for strength. 925 sterling silver is used for jewelry that isn't plated, dipped, or bonded. It's very durable but does tarnish if not worn or kept in a jewelry box or plastic bag-unless it has a Rhodium anti-tarnish finish. The 925 hallmark is the only one that can be called sterling silver. All other types of silver, are less pure silver and have more alloys, usually nickel, added to them. They have an 80% pure silver content and are sometimes labeled as German, Mexican or Alpaca silver. To see our large selection of 925 Sterling Silver, visit our eBay store Two Rivers Jewelry .