A gorgeous bike. Late 70s? Early 80s Ducati was in decline. They had a last ditch effort with the 500 Pantah. Struggling they produced the 651 track bike for the then new "Twins" competition. The north American market did not respond.
Ducati took the 651 frame, shortened the fork, lengthened the shock to achieve a then fashionable 26-27 degree fork angle and pushed the displacement to 900. The 1st modern 900 SS. The rest is history.