Thanks; I did place this in Dodgy section, partially to give the regular section a break, for more 'balance', as it were.
Serious thought, in regards to GOLD detection, being a non-ferrous metal, is to (contemplate) what sorts of energetic particles can be emitted, for some alternative detection.
Since that avenue is a big motivation, also perhaps much of conventional jewelry has some ferrous backing or framing. Thus there being an avenue for success, in probes underwater, near land.
Of course, a SAFE would likely have ferrous walls, even if containing gold bars.
And, since I'm into limited, single purpose circuits, a metal detector enthusiast could tell an interesting tale. Plus a circuit would be nice to read about, especially novel circuits.