From Dark Roasted Blend, a gallery of GM concept-bus designs built for an event called the "Parade of Progress": "One of twelve beauties built by General Motors, this is a self-contained display and transport vehicle created by the GM design staff under Harley Earl's direction. Opening side, lighting, retractable stage, distinctive center 'cupola' cockpit driving position and dual wheel front axle. Used in the 'Parade of Progress' touring exhibit created by 'Boss' Kettering that complemented the GM 'Motoramas' from 1940 through 1956."
Vintage & Modern Concept Buses
(Thanks, Salimfadhley, via Submitterator!)