Regarding the Monon car, this is the first series of cars delivered in this scheme that i can find.  The Monon also had a similar series of hoppers delivered in 1940 numbered 41500-41699.  These cars eventually had the same paint and lettering as your car, but the earliest date I see on the photos I have with this scheme is 1955. As I say the cars were similar, the 1954 cars were AAR standard while the 1940 cars were a Pullman variation on the AAR design, so not a great trade at any rate.

Regards,

Mike Aufderheide