The instructions in the kit were dated June of 1970. I have not seen anyone who offers a CS tag and this is an NOS tag and valve. The so called exact reproduction valves do not have these Factory markings.
Would be a very unique piece for that point judged car. Please don't fall for sellers listing repos as NOS. The item "1970 70 1971 71 1972 1973 1974 CORVETTE TRANS AM CAMARO NOS NCRS BRAKE BOOSTER" is in sale since Sunday, February 7, 2021.
This item is in the category "eBay Motors\Parts & Accessories\Car & Truck Parts & Accessories\Brakes & Brake Parts\Other Brake Parts". The seller is "ravjudge" and is located in Le Mars, Iowa. This item can be shipped to United States.