Often times , electro-plated materials will wear away from the surface (from polishing,cleaning,environmental effects & etc.) they've been deposited upon & one will see the metal(s) under the plating ... these 'base metals' usually differ from the original platings' appearance , esp when polished-up .
Sometimes there will be other metals (besides the main one/ones an item is made from) electroplated on the surface of the original metal such as nickle , copper & brass , and then the surface of this metal-plating is electroplated with silver , gold , etc. as the 'finish' coating on the surface .
Heavy polishing on these items sometimes will reveal , over time , a multi-layered (& colored!) surface that can be rather unattractive .
Many folks who sell older EP wares avoid polishing them , as doing so would make many buyers go the other way .
You're not alone in hearing many 'things' about EP items , capot1948 !!!