When stamped into silver, 925 commonly indicates the object is made of sterling silver. The stamp gives information about the metal composition, time and the item's country of origin. Sterling silver is generally composed of 92.5 percent silver, hence 925.
Hallmarks have been used to identify the purity of metals since the 14th century in England and France. The type of hallmark depends on the item's country of manufacture. For example, in France, a complicated system of symbols rather than numbers reveals the purity, place and time period of manufacture. A true hallmark is a guarantee of purity given by an entity other than the maker.
In the United States, true hallmarks are not used. A mark of fineness, such as the 925 mark, is often used with a maker's mark and a copyright stamp to guarantee the purity and authenticity of a silver object.