Are you sure about that, Bodde? I think that one was a Maestro PS-1a Phase Shifter – a six-stage. Beautiful phaser … I had one for years, and stupidly got rid of it, when I was downsizing. Only 3 fixed speeds – if you discount the ‘inertia’ ramping – so it should be easy enough to nail down the rate (probably SLOW PHASE, or possibly MEDIUM PHASE).
FETs, and no true bypass, so a simulation might benefit from a little tube-style distortion, and high EQ rolloff / lowpass filtering. We’d be trying to duplicate a unique Oberheim analog(ue) design here, but I’ll give it a shot when I get back in front of my pedalboard.