We researched them for Illegal Of The Day CA 10 posted on 2/14/14.

They were in Hertz's book of United States Playing Card Company records, printed in 2001 as CG. Fast forward to 2012 when I obtained a copy of the USPC records and was getting them ready to upload to the Chip Guide.
http://chipguide.themogh.org/cg_uspc_list.php

I saw no reason to doubt and in fact agreed with the CG on the chips. The C is dominant and the G is much smaller. Fast forward to 2013 when Bud found them. They were in the original USPC chip boxes with the monogram on the boxes. They were stamped GTC. Do you see the T? Sideways and very small. I considered a company logo but could not find one to match. IMO that leaves a personnel game set of 200 of 5 colors. How about Carl T Good? Good as guess as any.

I asked our "Friend Of The Hobby" to take a look. He found information on the H.S Crocker company that ordered the chips for resale but old GTC is still a mystery.