These models are Norfolk and Western reskins of the payware Britkits USRA Mallet 2-6-6-2 and the 12-wheel Tender included in the freeware Extra Tenders package. You can download both here:
http://dickyjim.com/steam.html
The Norfolk & Western's introduction to high horsepower steam designs began with its fleet of 2-6-6-2's, listed under the heading of Class Z, and assigned road numbers 1300-1489. The company needed larger, more powerful locomotives to handle the heavy tonnage passing over the stiff Appalachian grades found in southern West Virginia.
Unzip and install using the included RW_AssetSetup.exe installer. Copy all the GeoPcDx files from Assets\Britkits\Steam\RailVehicles\USRA_2-6-6-2\Default\Engine and paste them into Assets\Britkits\Steam\RailVehicles\USRA_2-6-6-2\NW\Engine.
In the scenario editor the locos are listed as: NW 2-6-6-2 a (b). They are installed into: Assets\Britkits\Steam\ RailVehicles\USRA_2-6-6-2\NW. The 12-wheel tender is listed as: 12 wheel Tender NW. It is installed into: Assets\Britkits\Steam\RailVehicles\NW_Tenders.
I used the Norvegan font from http://www.railsimstuff.com/fonts2.html
This package is released as freeware. You can do whatever you wish with it EXCEPT make money with its use.
Harry R. Adkins
December 2023