I have made a few pictures of a chinese detector sold under many names. It is a simple non motion machine with a small coil. It does not go deeper than 10 - 15 cm on a coin, but I got it really cheap. To my surprise it seems to be well made.
http://s1203.photobucket.com/albums/...leman%20CS120/
http://s1203.photobucket.com/albums/...leman%20CS120/