Smiths Autopilot controller. Conveniently sited on the retractable fuel tray panel about as far away from the instrument panel as possible. Hence the differently shaped knobs which you could identify by touch.
The aircraft was quite lively in Track, with LOC+GP on the MFS, but settled down once on the glide path with the Glide knob pulled.
You weren't supposed to fly with HRS steering on the approach. But the HRS was much more deadbeat than the MFS - you could get into a divergent lateral motion chasing the ADP at the same rate as the compass 'dot-crossing' rate in MFS if you weren't careful to let it damp out. So one dark wet night my captain elected to fly a PAR with the Nav Plotter controlling the HRS steer signal and it worked like a charm.
I've heard of people TFR'ing with HRS and Track, but with the E(levator) channel out. The autopilot looked after lateral navigation and they followed the MFS pitch pointer manually. I never tried that - we always flew manually at low level even though the aircraft was quite heavy in roll.