There is a section on disc repair in Arthur W.J.G. Ord-Hume's book,
"Restoring Musical Boxes" copyright 1980, George Allen & Unwin,
London, Boston, and Sydney.

Starting on page 128 he discusses rust removal.  On pages 129 through
137 he discusses and illustrates several different types of disc
projections, and different repair methods.

Jack M. Conway, Los Angeles, California USA