JP and Fred - you are very funny guys.
As to metal box vs wood. In my experiments with this my reasoning was that measuring the changes in the local electrostatic field was my goal at that time. So having a ground plane with the antenna pointing out from it, but not connected, gave me a way to see relative E-field differences. The wood box afforded no protection within the circuit so the local ES field was not really measurable as there was no fixed relation between ground and ES antenna charge detection.
What I really discovered in the field is ES is a poor way to look for treasure. I was able to show that ES fields are everywhere. All the bushes have ES field. So do the trees. Every step i took elicited ES response as the rubbing of grains of sand by my stepping on them generated sufficient response in the ES detector. And on and on.
Then I went to detection of ions (a new circuit). The sand thing still bothered this type of detector.
So telling me Mine Oro boxes used this type of box or that is really nonsense.
I did learn a lot about ES detection. Not sure if that was a plus.
If someone was to ask me (which is unlikely) what is the best possibility for passive LRL I'd likely answer magnetic anomalies. The reason - gold is mildly anti-magnetic. Any large concentration of gold should produce a measurable magnetic difference to the local magnetic field. If someone would like to supply me with a couple of hundred ounces of gold so I can test this theory I would be electrostatic er ecstatic.
Goldfinder