Here is an AGW article from the 1980's, where Ken Turner mentions his first airgun that he made in 1981:
https://www.dropbox.com/s/rhvib97m96...urner.pdf?dl=0
It was completed in 1982, I know this, as I own it and it has a date stamped on it:
https://www.dropbox.com/s/1we2g0wnhr...15413.jpg?dl=0
As mentioned in the article, Ken started making his first break barrel from scratch that year with a barrel latch (like the Mach 1), and steel shims on each side of the breech bolt and pivot bolt (Sound familiar? This was an improvement made by Venom to the HW80s, and probably used on the Mach 1). In 1982 I believe Ken made an underlever prototype similar to the ProSport, hence predating Venom Mach 1 or 2.
I am basing the dates on Geezer's post, can anyone confirm exactly when Mach 1 and 2 were first produced?