I first thougt the prototype

I first thougt the prototype for the Roundhouse 3-dome car might be the ACFX 4556 at the Railroad Museum of Pennsylvania: https://rrmuseumpa.org/wp-content/uploads/IMG_0674.jpg

Exhibit Label https://rrmuseumpa.org/wp-content/uploads/ACFX-Tank-Car.jpg

But the tank diameter seems smaller and the capacity of 80,000 lbs of the seems to be more appropriate for a 6,000 gal or 8,000 gal tank than a 4,550 gal one.

Looking further I found an article in Railmodel Journal about ACF 3-dome tank cars available on Trainlife.com: http://original.trainlife.com/magazines/pages/12/819/june-2008-page-15
/> Perhaps you can find the Roundhose car there.
Regards, Volker

Isn't The "New" Roundhouse Branding

Just redos of the Athearn Blue Box Line along with the MDC cars that they inherited ?

Just Thinnin,,

Espee over Donner

Vintage Athearn Tanks

If you are talking about those Athearn “blue box” tank cars that are now sold under the Roundhouse brand:

40' single dome tank            GATC SP O-50-13 undersize dome, and rivet errors, has 3 outlet valves?!

40' 3-dome tankcar            very oversized, no prototype as is

40' chemical tank car          Roughly 10,000 gallon insulated ICC 105 with very oversized top valve housing 

Having said that, they look halfway decent as generic sorta kinda reasonable tank cars, if you squint from a few feet away and don’t care about a prototype

my mistake

I guess that the reason there is no prototype info is that there isn't any specific prototype... I was apparently fooled by the fact that they're taking pre-orders for them, for delivery in September 2022. I mistakenly assumed that bluebox or bluebox-like cars didn't really work with year-in-advance preorders, and that these were some kind of less-rigorously detailed models of actual prototypes...

Roundhouse

Yes. The "RoundHouse" brand is now Athearn's "cheap" line of old Blue Box and MDC models that haven't received any special upgrades. Some of which may also not have specific prototypes, or be poor renditions, such as these cars.

So the cars we're talking about are the original Blue-Box tank cars moved to the Roundhouse label.

The old MDC-Roundhouse modern tank actually got re-worked and upgraded into Athearn's RTR line as the RTC 20,000 gallon tank.