Here I thought the clip style retainer was an aftermarket fix....who da' thunk it. Just never remember seeing or removing one from a car back in the day with the clip retainer, yet alone a blue one.
I believe a bulletin came out in 68 or 69 to use these because the retainers were coming off. I heard they came on some cars but not 100% sure of that. Probably a fix as needed thing is my guess.