These blotters from the Dale Hastin collection all relate to the C&NW 400, which was inaugurated on January 2, 1935. PDFs of the blotters are all around 300 to 400 KB in size.
Dated 1936, this appears to be the oldest of the four. Seven hours from Chicago to Minneapolis is just a bit more than 400 minutes, which is the source of the name. Even though it used heavyweight equipment, the train was competitive with the streamlined Burlington Twin Cities Zephyr and the steamlined Hiawatha.
The steam locomotive illustrated on this blotter suggests that it was printed before 1939, when C&NW replaced steam with General Motors E-3 Diesels on this route.
This blotter shows the Dieselized 400 a decade after the train was inaugurated.
Based on the colors, I suspect this blotter is from the post-war years. The North-Western Limited was discontinued in 1959, so it has to be from before that year.