While trying to look up photos of Differential Car Company trucks used under a C&O caboose, I came across this site, which had a page on the very similar "axleless" trucks used on industrial locomotives and cars from this firm.

The site is cool enough that I have to bring it to the attention of those here who are into such unique railways and their equipment.

http://americanindustrialmining.com/

The AIM guys are friends of mine. They are doing with mining and industrial railroading what I am doing with steel mill railroading.

AIM also has a coal mine exhibit at the Brownsville, PA showgrounds. Here is it in operation:

https://youtu.be/4B_YMdd-_H8

Glad you enjoyed that post!

Don't know if you're familiar with it (though I would almost guarantee the AIM people are), but there's an exhibition mine in Beckley, W.Va.--though it looks awfully tidy and clean for a coal mine!

https://beckley.org/general-information-coal-mine/

https://beckley.org/underground-tour/

https://www.youtube.com/watch?v=s6K91ElCTF4