The inscription "EPNS" on a piece of silver stands for electroplated nickel silver. This form of silver is created when a layer of pure silver is used to cover an alloy of zinc, nickel and copper during an electrochemical process.
British manufacturers invented electroplating processes in the 1830s and 1840s. One end product of this process, called hotel silver, was created to be used on trains and ships as well as in hotels and restaurants. A piece of hotel silver can stand up to much more abuse than sterling silver because the base metal underneath the silver is stronger than the silver itself.