This page from ST describe the car.
https://www.scaletrains.com/product/rivet-counter-ho-scale-bsc-f68ch-flat-car-trailer-train-as-delivered-ttmx-run-1/
RRpicture archives has some pictures.
http://www.rrpicturearchives.net/rsList.aspx?id=TTJX&cid=3
Mike.
My You Tube
The only 68' flat cars I was aware of were the DODX heavy duty for tanks and stuff. What were these cars used for? What kind of loads did they haul? I already have a collection 50' and 60' flat cars, so these are very interesting to me. I'm looking into buying some and adding my own loads.