I looked at these cars with interest. They appear to be updates of the 40 year old Walthers metal-sided "Shorty" passenger cars. The new Rivarossi cars appear to be based on the same C&NW prototypes as the old Walthers cars - full RPOs in the 9413-33 series, baggage cars in various 87xx series, combines in various batches in the 74xx series, and coaches in several groups numbered between 3088 and 3306 (the photos and car listing indicate Rivarossi used accurate numbers on the C&NW cars). The RPOs and baggage cars (with 6 wheel trucks) were in general passenger service, while the 4 wheel truck combines and coaches were used primarily (perhaps exclusively) in Chicago commuter service. The 4 car types would rarely have been used together, as the commuter runs did not carry RPOs, and the combines provided sufficient baggage space for the commuter trains. But with their similar appearance, they do look good together on a model RR, and particularly one with tighter curves. All the cars date from the 1920's. The 60' commuter cars were replaced and scrapped as the 85' bi-level cars began being delivered in 1956. I believe the many of the RPOs and baggage cars survived into the 1960s. Up until the mid-1950's, the C&NW Chicago commuter trains were being hauled by light pacifics in the E and E-1 classes, when they replaced by GP's and F's.
To my knowledge, neither the ATSF or CB&Q used 60' heavyweight combines or coaches. The RPOs and baggage cars were more ubiquitous and are probably like cars rostered by ATSF and CB&Q. All photos I recall of similar ATSF cars were "Pullman" green, as were CB&Q cars through WWII. Many older CB&Q head end cars were repainted an aluminum color in the 50's and 60's so they would not stand out so prominently when run in trains of fluted-side stainless steel cars. But even in the late 50's and early 60's, I remember a couple Q steam fan trips where they were still able to assemble a complete green heavyweight train - my few photos from those trips where my "people filter" was really working look just like old Lucius Beebe steam portraits. GQ