A few years back I read an online article by NASA Tom that set me on a journey to try to find the deepest detector around.
In his article, Tom discusses a project he undertook at the site of an old fort in Florida. You can read the original article here but the gist of it is that 95% of all desirable, non-ferrous targets (coins and relics and such) are still in the ground being maliciously masked by iron AND that there is a plethora of such targets at 12.5 – 14 inches deep!!
I know some of you don’t want to dig a 12 inch hole but if you do, take heart, your efforts are likely to be rewarded.