I have a few catalogs left from when I had my detector shop in in late '81-'83 in Utah and the CS/GCD was a short lived model that came oiut about '81 or '82 and died quickly. D-Tex was about finished and there were some gasping attempts to compete and keep it alive. They failed.
The Treasure King, Coin King, and Money King (TK, CK and M K) had been around for a few years, and the RS (Relic Search) models (100 and 200) were offered up in their camo scheme to appeal to the relic hunting crowd. These were in their 1980 catalog, except for the Cs/GCD which came along in '81 or '82. They also had the Money King motion-based discriminators, about '82, and then they dropped the CS/GCD and other models when they came out with their new body style with the stand-up contoured grip and "wart" buttons.
I recall a dealer/distributor trying to demo a new CS model and it wasn't very impressive. I know I didn't pick one up to carry. The 5" Omni coil that came standard on the CS was not workable on the CK or SK or RS models. I hope the one that sold was in good working order. it's always a gamble to invest in some of the older detectors, even when their appearance is very good, simply due to repair costs should they not function well.
Monte