Series 70 was a feature of both Government Model and Gold Cup, and the collet bushing/barrel combination remained well into Series 80 production, until 1988, at least.
All the original, full-size Series 70 and Gold Cup pistols had it. the Series 70 Commanders did not.
The "Series 70" model that Colt reintroduced about 10 years ago does not have a collet bushing. It's called "Series 70" because it doesn't have the Series 80 firing pin safety.