The Seller responded to my question as follows:

"Hello!

Chips are graded on a 10 point scale. PGS is the only company grading chips. The
scale they developed uses commonly accepted grading criteria. We really like
the grading! Keeps from buying overgraded chips from dealers who mis-state the
true grade.

Thanks!"

I emailed him back with the following

Thnak you for your response.

But as a long time collector I am not familiar with any commonly accepted
grading criteria for chips, and the PGS website does not even maentionchips
much less explain their grading system.

I certainly can't purchase a chip with a meaningless grade it would be like
buying an ungraded chip but paying extra.

Peter Sanders