American Machine-Made Marbles says they made opaque swirls, but attributes that information to Dennis Webb (and says no individual Bogard swirls had been identified as such). It seems a little out of line with what is said in the main text of the Bogard chapter. So where did Webb get the information? Was it from seeing what was in bags, or was it from talking to someone who worked at Bogard.
And heck, isn't Jack Bogard still alive? He certainly was when AMMM was written.
Yeah, do that!