After reading the various responses to the photo, I will add my thoughts. In the late '50's and early '60's the Burlington passenger dept. ran special week-end sightseeing tours from Chicago to Savanna, East Dubuque and Praire du Chien. Many of them came out on the Saturday AM Twin and returned on the SB AM Twin on Sunday. These tours were very popular in the fall, but did on occasion run at other times as well IIRC.
I was a high school student working at one of the 'attractions' at the Praire du Chien destination from 1960-1962. These trips seemed to be very popular with Chicagoans taking families out of the city, many of whom did not own cars at the time. We loved the Burlington Tours as the people were always very nice and tipped very well. On one occasion, a Burlington traffic rep was along on the off train excursions and I asked him what equipment they used and the reply was "anything in the coach yard ready to go, could be domes or flat top coaches". The tour cars ran on the regular Twin Zephyr and the tours could require anywhere from two to four (or more) extra cars.
Judging by the leafs on the trees and the light angles, it would appear that this COULD be a SB AM Twin with a tour consist on a Sunday at its stop at Savanna.
Bob