There's another video I watched from this production company of a museum-quality HO layout, I don't know if it's featured here in this video, but enjoy.
The above photo is a publicity photo. On the Southern Pacific, timetabled trains were numbered, so if this was on a numbered passenger train, the numberboards flanking the headlight would show the train number, not the engine's number, 4426. If the train were an 'extra' train (not timetable numbered), there would be an 'X' in the leftmost position of each of the number boards, then the engine's number, as in 'X4426.'