Since Sterling silver contains 92.5% mass of silver, and 7.5% of one or more other metals, it is considered a precious metal. Copper is the most common metal added to silver to create the sterling alloy. The standard minimum millennial (parts per thousandth) fineness of Sterling silver is 925 or 925 parts of every thousand is pure silver. Alloys such as copper are added because pure silver is too soft for most uses. That being said, the first legal definition of sterling silver jewelry dates back to 1275 during the reign of Edward I of England. The statute stated that a 12-ounce coin would contain 11 ounces and 2.25 pennyweights (a little more than a tenth of an ounce) and 17.75 pennyweights of some alloy. Markings such as "925", ".925" or "S925" are official stamps used to determine that metal is Sterling silver and without these stamps (except handmade items) can sometimes indicate that the jewelry purity is not solid Sterling ...