It would help to destinguish which 70mm mix you mean because according to imdb there was a 70mm 6 track dts of the special edition. Probably only seen in like 2 theaters though,lol.
I do know it was shown i believe at the Royal Premiere in London England.
And at the US premiere. It was not at Grauman's Chinese.
Can't remember the name of the theater its the place they had the premiere for return of the jedi in 1983.