I did a Newspapers.com search and came up empty on the Traveler's Wagon but got some hits for the Special Delivery.
The earliest I found was an article in the January 6th 1931 Detroit Free Press, nothing in 1930. It is part of a larger article and starts at the bottom of a column and is split across another but here it is.
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Throughout the rest of 1931 there are several references to the Special Delivery in an article about the 23 new Commercial Body types. This one is from The Wilkes Barre Tribune, May 8th, 1931.
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Other than some used car ads I don't see anything on the Special Deliveries in 1932.
Back in 2013 I helped Jerry Dewitt pull a Special Delivery out of Vernon Burke's pole barn. The unrestored one that Tim Kelly owned was very impressive the construction of the body and how well it was made was evident throughout. They are a unique and cool vehicle.
-Tim