Bros Silver Plate

how can i tell if silverware is actually silver?
someone recently gave me a set of sliverware, and i would like to know how to tell if its real siver. the knives say stainless on the blade, but none of the other pieces do. i think they may be Silver Plated. the backs of the pieces say this: 1847 Rogers Bros. then a capitol I S. the i and the s are in squares. any help?
Sounds like a nice set of Silverplate.
You can get help identifying the pattern at www.replacements.com
Great people there!