Seafoid, your photo came through great. They are beautiful cars.
If the numbering for the Pennsylvania cars followed the same pattern as my Black Diamond cars, then #1780 would have been for the combination; 1781 and 1782 are your two different coaches; #1783 would be the diner; and 1784 is your observation. Whether or not the other cars were actually made in the Penn set I do not know. In any case, your three make a great set that is plenty to haul around a standard gauge layout!
Daniels made a matching Pennsylvania standard gauge GG-1 to pull these with. Like the cars, there were not many made, but they do come up for sale now and then.
david