The earliest American Models heavy weight passenger cars required pushing the tabs both inward and upward to release the roof. The fit is very tight, so I usually by pushing in/up on each of the three pairs enough to get them started, then concentrated on trying to lift up one end of the car slightly so that--little by little--the rest would follow. It does take some time. Although it may take a couple of minutes for each car, I spent almost half an hour on one NASG Pullman sleeper before I realized this one had screws holding down each end. If you have problems, check to see if there are screws below the vestibule floors.
