When operators other than Greyhound showed interest in 41-passenger diesels after the war, GM responded with its model PDA-4101. Mechanically similar to the PD-3751 and -4151, its styling set it apart from the models built for Greyhound. Some of the 335 built had 45 non-reclining seats instead of the customary 41 recliners. The distinctive drumhead rear-end styling emulated the railroad observation cars of the time.
Information from the Bus World Encyclopedia of Buses – 1988