Archie - Don't know when you last bought a gold coin or when it was minted but these days gold coins minted by the U.S. Mint are .999 or if minted by Canada they will be .9999 pure, I dought you could refine gold to be 100 % pure but I could be wrong. Modern gold that is .999 or .9999 and is advertised everywhere to be 24 kt.
Both you and Richard maybe right in your statements but what difference does it really make.
Just my thoughts
Walt