Plated would be my guess. I bought a "silver washed" medallion from the White Sands National Monument about a year ago. It cost me $10 but is a pretty neat memento of the trip. It looks like silver because the surface layer is silver. What's under that, who knows? I haven't tried a magnet on it but that would be my 1st test of an unknown coin. There are a number of tests for silver but, unfortunately, most of them are destructive. Non-destructive physical tests such as specific gravity are also good but not as specific as a good chemical test. There are times when a Tri-corder would be SO handy!