I am a moderator at the IPF Poker Forum. "Citytom" has just posted a very interesting analysis listing the weights of 47 different casino chips. Obviously I have not verified these weights, but I have no reason to doubt them either. It seems that there is not really a "standard" weight for casino quality chips. Perhaps the variances are due to some chips being more worn than others........who knows.
http://www.ipfpoker.com/forum/about105.html
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Best Regards,
Murph