Well, this is something we've not been able to nail down definitively, as yet. Late-ish 1970s is as close as we've come.

This past thread has some discussion about the matter; https://www.outdoorking-forum.com.au/forum/ubbthreads.php/ubb/showflat/Number/78656/

This Victa Tech Bulletin shows 125's still being produced as of late 1977; https://www.outdoorking-forum.com.au/forum/ubbthreads.php/topics/38893

And this brochure which CyberJack has dated as ca. 1976 lists several 125cc models with the G4; https://www.outdoorking-forum.com.au/forum/ubbthreads.php/topics/86755

Cheers,
Gadge

"ODK Mods can explain it to you, but they can't understand it for you..."

"Crazy can be medicated, ignorance can be educated - but there is no cure for stupid..."