Sarge,
I bought a number of 2 oz US "copy" coins and returned the ones that were not marked .999 silver. If it it's not marked .999 silver, stay way from it or price adjust accordingly. Your findings are news to me. I originally thought all $20s were .999 pure silver then later came understand the $20s have a copper center and silver ring. It is very concerning to hear the AC $20s are not silver at all especially considering sliver was at $4 an oz when they were minted.