Sheffield plate utilizes copper and silver fused together in porportions of approximately 1 part silver to 12 parts copper which is rolled into sheets and then fashioned into items.
Electroplate involves making an item in a base metal, usually nickel and then coating the item with silver by electrolosis and then polishing.
Some electroplating was done using a zinc based metal composite. Because zinc is softer, it is easier to mold, but it corrodes and maybe won't stand up the way you'd like. But if you’re in love with the piece, there is always pleasure in just owning something.
More in depth information to follow.