This patent shows Shimano's somewhat feeble response to SunTour's sophisticated, but doomed, SunTour Superbe Tech design. You can feel that Masashi Nagano was not really interested, and I believe this design was never produced.
Browse associated derailleurs.
SunTour GranTech 1985?
SunTour Superbe Tech GTL (5400) 1983
SunTour Superbe Tech L (4800) 1983