That H-K tuner that was in the hifi I’ve been talking about had an AM - FM stereo mode, as it had separate tuning dials for each band. It also had a swith position labeled “FM-MPX” which needed an accessory module (the thing had tubes in it, and I never actually had the chance to dig into it - too you g at the time).This kind of stereo was provided in receivers made before the FCC approved the Zenith-GE system of stereo broadcast.
In addition to a position for a forthcoming demodulator for whichever system won, these tuners could play stereo sent by:
- An AM station and an FM station
- Two FM stations
- Mono
I believe it had a stereo preamp, so stereo (real stereo, not just band steering crap) records were known at the time.