I would be tempted to at least wind a couple of 20t 12" coils and see if it works as a dual coil Treasure Hunter (metal detector) project

I did do that - well not exactly as I used 8" coils with 18t (after my quick & dirty 2 coil experiment discussed previously) and got a very similar result in that the 'detection' of metal objects caused meter movement and high pitch oscillation through the speaker but did so with objects further away from the coils. So it does definitely detect metal objects to some degree. That however tells me it could be a simple metal detector but I suspect it may be a bit more intelligent than that in that it may have been able to identify different types of metal (ferrous or otherwise) or other variations. As I have put a lot of effort researching this object for some time now and have not been able to definitively identify the purpose or source of it I have to confess I have lost interest. As I have said, I think the missing (& probably specialist) 'probes' were vital parts of the device.

 

Save the circuit board assemblies as well, it seems that it may have the makings of a UHF transmitter/receiver package. That might be handy if you ever become interested in Ham Radio.( aka Amateur Radio)

 

Save the circuit board assemblies as well, it seems that it may have the makings of a UHF transmitter/receiver package. That might be handy if you ever become interested in Ham Radio.( aka Amateur Radio)

Yeah, will do as there are no particularly useful components to me on there , just a 555, a NAND gate and an LM386-4 and some passives, all of which I already have.

 

Given the health warnings about high-power NLJD devices, I would avoid turning it on with any kind of probe attached. Without technical documentation, as that I can say is that it's likely that this device, as a non-civilian release, was greater than the 'low power' general public device.

 

it does definitely detect metal objects

It detects dissimilar metal junctions - read https://en.wikipedia.org/wiki/Nonlinear_junction_detector.

 

Given the health warnings about high-power NLJD devices, I would avoid turning it on with any kind of probe attached. Without technical documentation, as that I can say is that it's likely that this device, as a non-civilian release, was greater than the 'low power' general public device.

It did not have the appearance of anything close to even a moderate power device, Not as much power as a cell phone, even. Thus no hazard.

 

If it is a NLJD and it responds to ordinary metallic objects, then it is pretty useless.