it's magic The Nakamichi Dragon had a split right channel gap, and it would monitor the two signals coming from the same (right) channel looking for phase differences. The playback head would then be adjusted to result in 0 phase misalignment. This relies on poor azimuth resulting in phase error in a mono signal. It only did this at the start of the tape or at the start of a new segment...
I don't know if there were other systems that performed auto-azimuth control in a different way.
It is highly likely, Peter, that your Revox does auto-bias correction, which doesn't require the mechanical repositioning of the head.
Damn fine machine you've got there though. You really should use it (a lot!!).