A 925 stamp inside a silver-colored ring means the ring is made of sterling silver, but inside a gold-colored ring, it means the ring is made of Vermeil, which is gold-plated silver. The 925 stamp is an international industry standard.
A metal stamped with the numbers 925 is internationally recognized as being made of sterling silver. These numbers indicate that the metal consists of 92.5 percent silver. An alternative stamp for this metal are the words "sterling silver." A Vermeil ring may look like gold, but it actually consists of a sterling-silver base with a gold plating or coat. Silver-colored jewelry without either of these stamps is probably nickel silver or German silver, which do not contain real silver.