but we don't officially know that yet.
it could have been a lot of railroads.
it could have been one of the following.
those where some of the possible ones i was thinking about.
decied which one(s) in this list sounds like it would be mostly used on
What did you use to base your list of possible railroads? Many if not most of those either had their own in house leasing unit, such as CRIP, NYC, & CB&Q, or an affiliation and partnership such as PFE, ART, or Western Fruit Express. I do not think I have ever seen a photo of any URTX car for the lines you list - not to say it was not impossible.
URTX was based in Milwaukee as was the Milwaukee Road and MILW leased many many such cars - the evidence is firm on that.
Sure - if we were model railroaders we could paint it anything we wanted. How about Conrail blue? Some modelers even paint opposite sides in two different schemes or for two different railroads! The guys in the freight department and most others at IRM are obsessive compulsive about historical accuracy as to all the details, minute lettering and very detailed color history and matching. Part of our mission is to preserve the history here, not re-write it.
You are correct that the Soo Line leased URTX cars and we have one such car in the collection. But it is nothing like the car we are discussing. After at last finding a photo car in the same series as ours that displays a herald (many of the leased cars did not) I think the question has been answered.