How Can You Tell If 100 Yr. Old Flatware Is Silver Or Silver-plated?

I think it is called a continuity check an appraiser will run a low voltage through the item and see what the resistance level of the material is.pure silver or mostly silver flatware will have less resistance than the cheaper plated silverware. I think this is how they test it in order not to damage the silverware. That and they can check for the indentifying marks or makers trademark/foundry stamp to determine age and the time period that silver plating was used in the production of silverware.this is all i can think of right now without googling how to appraise silverware.