We have all seen plenty of sporter CETME rifles and civilian HK-91s, but when the G3 was new to the Germany military, there was already an interest in bringing semiauto versions into the US.
The Golden State Arms Corporation was the first to do so, with three batches of imports in 1962 (just 3 years after the G3 was adopted).
The first of these came into the US in March, and was basically identical to the military G3 except with a two-position semiauto-only fire control pack.
Later imports had to be made more and more distinct from the military G3s, which leaves these 3/62 guns as the closest thing to the real G3 available to the non-NFA US shooter.
Video ont he development of the roller-delayed blowback system: