Correct, it began on a PDP-7 in embryonic form, and having proved the point to management, justified buying a PDP-11, which was then the primary Unix machine at

Correct, it began on a PDP-7 in embryonic form, and having proved the point to management, justified buying a PDP-11, which was then the primary Unix machine at Bell Labs for some years, certainly through Version 7 / 7th Edition, which was around the point when people started porting it to other architectures. Right around then, Berkeley BSD development mostly shifted from PDP 11 to the DEC Vax 11/780.