Yesterday while looking because of some MD-price
I found the following ebook here - it's for free !!
http://www.nuggets.at/Metalldetektoren_s2
Scroll down a lil' bit and on the left side you will see
the free download link for the pdf (see attachment).

It's in german language but you can export the pdf
as a txt file and afterwards translate it with google.
The ebook also contains very interesting pictures !
I found the following ebook here - it's for free !!

http://www.nuggets.at/Metalldetektoren_s2
Scroll down a lil' bit and on the left side you will see
the free download link for the pdf (see attachment).
It's in german language but you can export the pdf
as a txt file and afterwards translate it with google.
The ebook also contains very interesting pictures !