At some point late in its corporate life, K-line manufactured a line of S-gauge freight cars that used 3/16"-scale car bodies (perhaps made from the old Marx dies they had). They had a nice line of diecast S-gauge trucks which they mounted under them, and the result wasn't too bad:
The cars featured nice graphics, and included opening doors and wire handrails on some pieces. They look quite different from Flyer and Lionel production, but were a nice alternative to the pricey Flyer-licensed product.
I don't think this one ever got any track-time.