Stephen,
Have any of your students had a chance to see the museum? One of the design team on this VTR was Ray Dolby, yep same guy. When I started, we only used this machine when nothing else would do or we needed heat. Our other machines were 1200 and 2000 series machines. However, when we started producing Soundstage, we need to record in stereo. Ampex had no interest at the time so we developed two methods. One involved recording the second channel on the cue track. This required a 240 Hz notch filter to cut out the adjacent control track but the 960 Hz video track still got into the channel. We then modified a two track head and installed it in place of the mono head on a special audio block using Inovonics stereo record amps with Dolby B noise reduction. As you know Ampex eventually thought ours was a good idea and added it to the AVR 2 and subsequent production machines. We eventually added Dolby A when it became available to all of our machines and Dolby made a card for our C series decks that became standard options in the VPR2. The VPR 80 didn't have enough room so the Dolby frames were external.
See here for the discussion of Quadraplex recording.
http://en.wikipedia.org/wiki/Quadruplex_videotape