Prototype Found?
Received this photo from the Wayne Historical Society and the following info:

This Station is from Wayne, IL built by a local Horse Farmer and the plans were from Frost & Granger. The Railroad at Wayne is the Chicago & North Western. The Station is being repaired for use as a Museum 15 foot from the enclosed photo.

Sure looks the part for the model kit prototype and for the CP&W, although the CP&W looks to have made a few small alterations to the plan. Guess the old CP&W brochure was a little off on the location, not in the Dakotas as stated but in Wayne, Illinois.

No wonder I can never remember seeing this depot in Wayne... it was moved away from the tracks in the fifties:

http://waynepreservationsociety.weebly.com/depot.html

Frost & Granger was an architectural firm that did a lot of work for the C&NW, as I recall, one of the principals was the son-in-law of some high ranking official on the NorthWestern. Typically, once a railroad designed a depot, they tended to use the plan over and over, until styles changed and they designed something new, so it's not unreasonable to expect other similar buildings elsewhere on the road.