A 3rd option: Oswald left the steps about 15 secs post shots and went westward to the SW corner of TSBD, then northward along the west side of TSBD to enter the west side door of the loading dock (annex).
He then entered TSBD from the loading dock annex via the roll up door right beside the rear staircase and elevators and he went up the rear stairs to the 2nd floor lunchroom.
The purpose most likely to retrieve a jacket , which he would have on when he got into Whaleys taxi . It was probably the gray jacket which Oswald had worn to work that Friday when he got the ride with BW Frazier.
Oswald may therefore, have been at the 2nd floor lunchroom door and was In the small vestibule area when Baker arrived to the landing at about 80 sec post shots.
Oswald Leaving the front steps of TSBD at about 15 secs post shots from the steps, and walking at pace of 5ft/sec about 240 ft approx in 30 secs , then up 18 steps in about 15 secs, then across the landing another 15 ft and thru 2 doors about 5 secs then into the lunchroom some distance , retrieve jacket and put it on, turn around and go back out, about 10-15 secs, thus about 75-80 secs post shots , Oswald is meeting Baker/Truly on the 2nd floor landing or just as Oswald’s in the vestibule about to either go down outer hallway or exit out onto the 2nd floor landing to go back down the rear staircase.