I always store my musical box discs in heavy duty PVC storage bags.
I then store the bags standing up on the floor between instruments
or of a shelf if a smaller size.  If you put a piece of corrugated
cardboard in the bag you can store two discs in each bag with titles
clearly visible through the clear bag.

I currently have many 100's of spare storage bags for sale suitable
for:-

  Polyphon 11 inch  (or 12 inch other makes)
  Polyphon  15-1/2 inch (or 16 inch other makes)
  Polyphon 19-5/8 inch (or 20 inch other makes).

I sell them in 10's.  If you would like price & postage details just
let me know what country you live in and which currency you would like
me to quote in.

I am Kevin McElhone, Northampton, England.