The letters EPNS indicate that a piece of silver has been electroplated. In electroplating, a thin layer of liquid sliver is applied over the surface of an item made of a base metal. In EPNS silver, the base item is most often made of nickel.
When an item has been electroplated, the amount of silver used in its construction is very small. When electroplated items are appraised for value, the final price is usually based more on the item's design rather than its value as a piece of precious metal. EPNS markings are usually found etched into the surface of the item on the bottom or the back.