Historically, silver plating was used as an affordable alternative for people that could not afford sterling silver pieces. In many cases, these pieces are hard to differentiate from sterling silver, but one of the easiest ways to tell the difference is the presence of a hallmark. Sterling silver pieces will be adorned with a numeric hallmark (925 or .925), the actual words “Sterling Silver”, or a lion hallmark.
Without a stamp, there are other ways to tell if your item is sterling or simply silver plated. A strong magnet can be a great tool, as silver has weak magnetic effects. If a magnet sticks to your item strongly, you should feel confident that it is only silver plated and contains more of another metal.