Unlike the previous NP stationery from the heavyweight era, this one doesn’t mention air condition or roller bearings, so it must be from the 1920s or early 1930s.
The image of the steam locomotive on the letterhead doesn’t show the wheels, and from the front the first NP 4-8-4 locomotives (which were built in 1927) looked very similar to the NP’s earlier 4-6-2 locomotives. One difference was in the pilot (“cowcatcher”): the 4-6-2s appear to have had more slats than the 4-8-4s, though this could change as wooden pilots were rebuilt from time to time and neither had as many as appear in the above drawing.
This envelope is similar except for the steam locomotive. I presume they were used together in the club cars of the North Coast Limited and other fine NP trains.