Something about the headlights gave it away. In any case, I found another link that gives a clear definition to some of these walk-in delivery vans. Somewhere in this PDF link to Vintage Truck Magazine, there's an article on the Hudson Business Car, which is not an actual car at all.
http://vintagetruckmagazine.com/pdfs/VT13-5.pdf

Hmm, maybe this post should be transferred to the "Useful Links" section.