I don't have those, thank you though. I took it to a jeweler and he didn't really help. He said he thought it was silver plated. No test, just a glance. I don't think it's plated because there are scratches on it and the inside seems to be the same metal. I think it may be pewter. Is this a possibility?
It's possible, if you asked a jeweler they have a lot of experience and a glance is often all it takes. If there are no markings on it, chances are it may be a silver plated charm or pendent - or just pewter. (Quality jewelry will almost always have a mark of some sort with all higher end jewelry bearing a hallmark)
Usually the plated stuff will have bubbles under the silver at least if its been in the ground a while where the other metal under it is starting to corrode, I bet its sterling though as it looks to be off of a charm bracelet. Some of the older stuff isn't marked, I found a bracelet once that was pretty old and most of the charms were marked but a couple wasn't. Some of the links were plated and most of the plating was gone and the metal underneath was corroded pretty bad but the unmarked charms were bright and shiny like yours. HH