The GS4 was essentially made by Kadar (Bachmann) for Lionel in the 70's. Still a nice loco and available in several versions under Bachmann.
Actually, the Bachmann GS4 was originally tooled for a company that never got off the ground, as I recall their name was either Lima Products or Lima Models. They ran a couple of ads in RMC in the early 70's. For whatever reason it was advertised, but never produced under that brand name.
Rusty