Unless it is stamped "STERLING", chances are good that it is just silver plate.
In order to identify if flatware and other items are sterling silver, the items must be identified with a hallmark or stamp that states “sterling” or “925”. The stamp is usually small and placed on the bottom of bowls and plates or at the end of flatware items. Items that are sterling silver mean that they are 92.5% silver. The stamp or hallmark on these items is mandatory by the United States government in order to keep silver regulated.