Nope, the base metal is what the silver is applied to, in this case it is an alloy called German Silver or Alpacca, this is the alloy of nickel, copper and zinc. Once the pieces are manufactured of this alloy, they are finished with an incredibly thin coating or plating of silver, hence the term silverplate.
It may help for you to have a look in the
Silver Glossaryunder Alpacca & Electroplating
regards, Tom