Ex pro car? Looks too be to be a standard body, even for a limousine. Rear door on the inside even looks like it was once and actual door, and removing the exterior body seams isn't that hard.
http://www.ebay.com/itm/Buick-Other-limousine-Limousine-luxury-vintage-antique-mini-bar-/131166002976?forcerrptr=true&hash=item1e8a1a5f20&item=131166002976&pt=US_Cars_Trucks
http://www.ebay.com/itm/Buick-Other-limousine-Limousine-luxury-vintage-antique-mini-bar-/131166002976?forcerrptr=true&hash=item1e8a1a5f20&item=131166002976&pt=US_Cars_Trucks