just go to PDGA approved discs
and this will give you an idea of when the discs was approved. Release date should be soon after that.
And at the time the Cheetah was a fast disc. Along with the whippet, viper, gazelle, cyclone. It wouldn't be until almost 5 years later before the advent of the Thunderbird, Valkyrie, Eagle (modern mold) Firebird, XS, XL etc..