This poster is a “Cartoon” which would have been used as a display if garages.
The 1951 Pontiac Chieftain, de-luxe four door Sedan was built by the Pontiac Motors Division of General Motors. This was an entirely new design, in fact the first since WWII.
The Chieftain replaced the Pontiac Torpedo and at first had 4 models: Sedan, Sedan Coupe, Business Coupe and Deluxe Convertible Coupe.