In response to Martin Tengström's question about how to make card
discs, I can give my experience.  I have made discs for Ariston 24-
and 36-note scales.  I make up the blank discs by gluing together,
in a press, three thicknesses of 180 gsm buff manila card.

The abbreviation "gsm" stands for grammes per square metre, and is the
internationally accepted measure of the weight of card and paper, and
is therefore a guide to its thickness.

I have this thickness readily at hand as I use it for Tanzbaer rolls
(in single thickness) and other small music books, etc, but you could
use two thicknesses of 270 gsm or even a single thickness of 540 gsm.
As a guide, one thickness of 180 gsm is around 9 thou [0.3 mm] thick.
(For metric persons, 40 thou is equal to 1 mm.)

There was quite a variation between thicknesses of original discs, from
around 25 thou up to 35 thou, but I find that the three thicknesses of
180 gsm, giving 27 thou, is relatively easy to punch and is quite strong
enough once shellacked.

Any competent stationery wholesaler will supply manila card in its
various weights, although you may have to buy at least 250 sheets at
A0 size.

Once you have made up the blank discs, you will need a purpose-built
punch in order to cut the disc.  A book music punch can be easily
converted to cut discs by the addition of a 'centre' on which to rotate
the disc, which is indexed in order to cut each track accurately.  Once
cut, the disc is shellacked in order to give strength to the ends of
each slot, which is where all the wear takes place.

Regards from GB,
Nicholas Simons