Metal Detector Frequencys?

[Arky 1]

what does the different frequency's of a metal detector have to do with the type of object it is detecting

[gregl01]

I'm no expert, but I think some metals react differently to different frequencies. Gold reacts better to higher frequency and coins somewhat lower? I have machines with different frequencies and they do seem to pick up some things differently. It seems my Tesoro that runs at 14.XXX actually hits small brass and copper really well. So I guess that the benefit, although the engineers try to find a happy medium so the machine will pick up all targets ok. I think it also can affect depth on certain metals?
Greg