Hello,
I have used the OKM future series Walkabout and the Exp 4000
they both work, that walkabout isn't no where near as good as the Exp 4000.
I have tested the Exp in black lava material known as Bassalt.
The Exp 4000 was able to show the target ( a gold target 2'X3' in base shape )
at a 35' depth. The depth feature on it is fairly accurate some of the time.
I already knew the depth of the target and shape before employing the
Exp 4000. It's an EMF Imager and in my opinion better for treasure hunting than a true GPR.
You just have to learn what it can and can not do then you wont be disappointed.
Accurate locator's sell EMF Imagers also that are cheaper but I don't like the lap top hanging around my neck while trying to survey rough terrain.
I have a test bed where I have tested the Walkabout extensively and it works but it takes a number of scans to get a couple of good ones.
Keep in mind I do not use either unit to find anything I only employ it on targets that I have already located.
The Exp belongs to a friend of mine and he seems to be happy with it.
Hope that helps. Kelly Brown