yes, it has been mentioned before. It is on my Embossed Mold Project site:
http://www.antiquegamblingchips.com/molddesign_manmade.htm#md77

Allan Myers, a dentist, long ago x-rayed a lot of the chips to show the metal pellet, and he had an article about it in the club newsletter.

In a day or two I will update my Christy and Jones entry to give info on the edge spot shape issue.

Robert