Looking back through what I've got from 1968, I'm going to give you this very vague response:
It depends.
Some are the "old" set which has the floor-to-ceiling posts by the bench as Mister Rogers enters, the Trolley track running in front of Picture Picture, and a shelf just to the right of Picture Picture.
Then there are others where the posts are short, the traffic light is moved forward, the tracks no longer run in front of Picture Picture, and/or the shelf is gone. Note that I said "and/or." Various episodes include various combinations of these things.
Suffice it to say, that out of the episodes I've seen from 1968, the set varies often.
Unfortunately, I don't have time right now to go through each one and detail exactly what the set looks like. Maybe someday...