er, but you could count Benton and Yates as 60's companions couldn't you? Certainly Benton was definitely around in Troughton's time. And the Brigadier is technically a 60s companion as well.
The Brig appeared in two serials in 1968, Benton in one. Not again until 1970 and the Pertwee era. All things considered, at most, that's like Donna's appearance in The Runaway Bride
before her becoming full-time, proper companion in Series Four. Even that's a stretch, especially in Benton's case. More like Wilf's cameo in Voyage of the Damned
, I'd say. But certainly until Spearhead From Space
there was no indication that either would ever be anything close to "companion status."
In either case, Yates wasn't around until Terror of the Autons