I had wondered about triple dome tanks also and where prototypically I might use the several single, two, and three, dome tank cars I had bought from SC&F purchased earlier other than overhead traffic.  That in addition to several Sunshine tank cars.  [Interesting fact: Presenting at an early Sunshine Naperville meet, Tricia offered to pay me (for presenting,) and I asked, Might I get paid in Sunshine cars instead of cash? The reply from Tricia was an emphatic Yes! in reply. It was Saturday morning so while the stock was partially depleted, a good selection was still available. On Thursday eve, I had rushed the room with many of you, so I had my "must haves". I looked around and found many cars that interested me, and off I walked with a full armload of Sunshine models that were an even sweeter deal than the cash.]  And no, none at this time are for sale. 

     I had posted to another group this collection: https://www.loc.gov/pictures/collection/coll/item/2004678115/
Here it is with the grouping open:   https://www.loc.gov/pictures/search/?q=LOT%201125&fi=number&op=PHRASE&va=exact&co!=coll&sg=true&st=gallery
And this grouping is presented for your perusal. Dated 1939-1941, it is chock full of single sheathed boxcars, boxcar roofs, several shots of an L&N ya'all boxcar - showing grain inspection being done, a RI SS truss rod boxcar next to an Ann Arbor SS, (plenty of grain doors in the foreground), several photos of two track vest-pocket engines houses, and yards, and yards full of Steam Freight car photos.  

In the group, four across and two down is a photo marked Coalyard, Minneapolis here: https://www.loc.gov/pictures/item/2017718340/resource/   
On the left are a string of tank cars of various sizes, and one triple dome. 


      An early Minneapolis landmark, the Foshay tower is above the locomotive tender. And of the steam locomotive, it appears to be a Chicago Great Western emblem. From the sun cast, this might be north-east of Minneapolis towards the Minneapolis/St. Paul border just north of University Avenue. Now under an office park.
And Rand Boyd covered several models in his March 1987 RMC article. 
However, I was surprised to see the 3-dome car. In reflection back to the original thread, my sentiments once I viewed a photo (with little trouble) of the offering, matches Bruce's. 

So, after you have grabbed your favorite beverage and opened the Lot above, Lot 1125 and found images like this:  Empty freight car, truck, grain elevator, Minneapolis, Minnesota (loc.gov)
(Does anyone offer a decal like this?)  This looks to be a Canadian Car (or Soo Line possibly?) Note the trust paint in this photo: https://www.loc.gov/pictures/item/2017809731/resource/

      Plug in 1126 to the Lot number and find more cars to view: https://www.loc.gov/pictures/search/?q=LOT+1126&sp=1&st=gallery
A nice side view of a coal loader, and if you found the photo of the coal loader and it does not match your Walthers model, the Walthers model is different, and accurate. See the attached photo.   Lehigh Valley DS boxcar here in the Twin Cities next to an NP box noticeably higher. https://www.loc.gov/pictures/item/2017809856/resource/       
  For my part, the NP box is in a 1918 class of 500 cars with a 10 foot inside height and all will be retired prior to 1950. Anyone want to take a stab at IDing the LV car? 

    Find in this grouping a load of farm tractors with rigging and blocking example ready for you to model: https://www.loc.gov/pictures/item/2017809858/resource/
In the photo of a flatcar load of corn shuckers, I find the interior of a drop bottom gondola in the lower left more interesting: https://www.loc.gov/pictures/item/2017809859/resource/ 
For those that have the Westerfield CMSP&P composite gondolas: https://www.loc.gov/pictures/item/2017718328/resource/  

Anyway, plenty STMFC content to see here. By John Vashon, and others.                                                                                        James Dick - Roseville, MN