Sterling silver is a term used to describe solid silver of 0.925 purity -- that is, silver that contains 925 parts of silver per 1000 parts. Silver-plated items have a thin coating of silver over a base metal body. Most silver-plated items are electro-plated nickel silver, or EPNS. An earlier mechanical process, known as "Sheffield plate," involved squeezing sheets of silver and copper together in presses. Follow these steps to distinguish sterling silver items from both types of silver-plated items.
Look first for a hallmark. This is a mark that is applied to a piece to indicate that it has reached a legal standard for solid silver; it is a guarantee of quality. Also look for the words "sterling" or "sterling silver" on modern pieces. British silver includes a hallmark that shows a lion walking sideways, known as the "lion passant." The presence of any of these marks is sure proof that the item is sterling silver.
Check the item for the letters "EP" or "A1." "EP" stands for "electroplated" and "A1" for best quality. The presence of either of these marks is a clear indication that the piece is EPNS or silver-plated. If the piece has no markings at all, follow the next step.
Scrutinise the piece carefully for signs of wear. Sterling silver, EPNS and Sheffield plate wear in very different ways. Because silver is a soft metal, the details of sterling silver items tend to blur after repeated rubbings while still retaining their original colour. On EPNS pieces, the outer layer of silver is thin and rubs away to reveal a pale yellow base metal. On Sheffield plate, the outer layer is slightly thicker, and the exposed copper body will be a rich brown colour. It is worth looking out for Sheffield plate, as it was made for a comparatively short period of time between 1745 and 1840. It is thus far less common and more valuable than EPNS, which was produced starting in the 1840s and is still made today.