William Sommerwerck wrote:
It may have been a quarter-track stereo machine.
These record two tracks in the same half of the tape
that a half track stereo machine uses for one track.


NOT SO! Quarter-track quarter-inch machines have interleaved, not adjacent,
stereo tracks.

For the OP, in case anyone didn't already know:

Side 1 L ---
Side 2 R ---
Side 1 R ---
Side 2 L ---

so a 1/2-track machine would get side 1 L and reverse side 2 R on its left
channel, etc, mixed more-or-less equally in the magnetic domain.