Hi Daniel,  The previous responses you received were both factual and
absolutely correct.  Please don't mess with the musical box mechanics
without a lot of further reading and study on the subject!

As suggestions that might be useful, try contacting

1. Australian Museum of Mechanical Music
   338 Botany Road, Alexandria, Sydney, N.S.W. 2015
   Craig Robson
   tel.: +61 2 9319 6666

2. South Australian Museum of Mechanical Music
   Barossa Valley, P.O. Box 24, Lyndoch S.A. 5351
   tel.: 61 (8) 8524-4014

3. Mechanical Music Society of Australia, Inc.,
   John Wolf, P.O. Box 101, Begrave, Vic., 3160

I'm sure if there are qualified music box restorers on your fair
continent; they will know who that might be and how to contact them.

I'd also suggest that you and your client check out this web page:
http://www.intertique.com/PurchasingMusicBoxPart4.html 

Good luck to you both.

Most sincerely,
Don Caine, Proprietor - The Music Box Repair Shop Unlimited
Lomita, California
Tel.: 1-310-534-1557
Fax: 1-310-534-1558