Ok, there is a book written by Pierre Beasse explaining how to use this pendullum.
The title of this book is:
'Instructions for the Use of Schumfell Radio-Magnetic Detector'
It is not easy to find but you will do if you really want it.
Also check the following link where you can find much info in some other book written from the same author.
http://books.google.gr/books?id=uS-M...page&q&f=false
Regards
g-sani