not many 70 coronets around, they were way over shadowed by the charger and outsold by Plymouth. 70 was really the last year for a pure coronet muscle car. 71 was the first year the coronet and charger were combined which is why we have a such thing as a 71 charger superbee.
Then in 72 it went on to being mostly a 4 door/wagon only until silently dying off in 76.
The coronet was an old name plate by then.