Well, I know there have been a few projects in Germany to restore
historical disks, and a professional company is doing it.  These
are the links:

  http://www.diamondcut.de/pages/info.html

and maybe you try the Fachhochschule Berlin (University of Applied
Science) where you can study restauration: <M.Knaut@rz.fhtw-berlin.de>

  http://www.f2.fhtw-berlin.de/f5/restaur/tkdiplom.htm
  http://www.fhtw-berlin.de/studg_fb5_3.html

Kind regards

Gerhard Dangel
Augustinermuseum, Freiburg