White lettered credits at the beginning would indicate that it is the theatrical edition. Plus, when Spock is on Vulcan, you can see T'Khut in the darkened sky.
I remembered the darkened sky and some other stuff from '79, but there've been so many versions ...

So the overture was in the original theatrical release? I thought I remembered it being there, but again, so many versions. And it's not there in the P+ version I just watched.I believe it had it going all the way back to its original release in 1979.
That was when you were suppose to drop your acid...