Hi Ron,
You get two tones with the Minelabs, a rising tone and a lowering tone. The hi tone is small items/weak signals and the low tone is large items/strong signals.
In practice this means bullets, most gold, nickels, and common aluminum gives a high tone, along with small nails, small flat steel, and wire.
The low tone is copper and silver coins and large iron. I'm not sure where buttons would read. You need to take all the relics you have and test them and separate in two piles, hi tone and lo tone. You will see a pattern develop.
The trick is be a contrarian. If the area is littered with tiny iron trash, only dig low tones. These would be belt buckles, plates, cannonballs, guns, and most coins. I treat the hi tones as a threashold sound and ignore it, waiting for the low tones. Run the volume low if the trash is too thick.
High tones would often be bullets but some of the larger bullets may go lo tone. I'm not sure. Gold is usually hi tone but if the gold is large enough it will go lo tone.
Do not use the smooth setting if using the tones as it mixes the tone responses. I've not had enough time to determine where the breaks are but it is different in smooth.
The tones are totally separate from the disc mode and work at full depth. They work with both mono and DD coils. The iron disc mode only works with DD coils and only on shallow targets. it is unreliable on many gold nuggets but may work better with bullets.
The three presets offer great room for experimentation. I'm going to try and set up multiple mode I can flick between to compare signals and get more of an idea what the item might be. Question - how might varying the gain affect the response on an iron target versus a non-ferrous target? Lots of things I need to try with the GPX.
If I were in relic country I'd be going crazy with a Minelab SD/GP unit. I think you are going to be amazed once you get the hang of it. I'd appreciate an email if you learn any tips you can fire back my way.
Steve Herschbach
steve@akmining.com