I once obtained a number of Polyphon zinc disks that had been stored
horizontally, on top of each other, with thin felt disks between.  Even
so, the note projections were badly flattened or bent out of shape.  It
took me many hours to repair or replace the broken projections, all the
time cursing the one who'd packed them flat.

I therefore believe the better way would be to store them vertically in
a sturdy box, in such a way that the projections won't catch on one
another.

When being played, the pressure bar and rollers hold that section of
the disk in contact with the star wheels so a slight amount of warping
is not a problem.

Colin MacKinnon