Great advice to crank the disc, at the start of learning. I know that as soon as any experts hear that anyone would knock out anything above iron, they shutter with disbelief. Ie.: "What about that $1 gold piece you might miss? or that tinsel-thin gold chain??" etc... But there are some environments where you just don't have that liberty, especially when you're trying to learn the machine. If a person only dug 1 or 2 coins per 100 targets, they would NEVER get the "recipe" down, because, those targets were soooo infrequent, that they would not pick up the similarities of sounds. Sometimes the best way to learn is to go to an easy place, where you can get back-to-back-to-back easy coin sounds (yes, even if it's clad) so that the "lights go on" in your brain, and all of the sudden, after the 50th clad, your ears are "in tune". Then you can lower the disc. to perhaps mid-range, and start digging the square tabs, larger aluminum shards, etc.... Then down to the lowest setting, etc... What will happen then is you will be able to discern what the machine is telling you on its TID scale, and recognize the iron vs lows vs the mids vs the highs as you're hearing them, since you learned each zone individually, rather than an unorganized symphony.
There may even be hunt sites where you would not want to go low disc, no matter how advanced you are. Or, at least, cherry pick based on what the TID is bouncing at. Places like junky parks may simply not be worth digging foil and such, so you may elect to go for the deep silver. Yes it's true that you might miss a gold ring, but if gold rings are your goal, you'd be much better off just going to a swimming beach, so as to have much less punishing ratios.
One time in my city, they demolished a rodeo grounds grandstands that dated back to the 1920s. Under the bleachers was hard-pan dirt, where for 70 years, people had pushed their trash through the slots of the seating, to rain down below. The trash would be picked up, but of course coins and individual tabs, etc.... would be lost in the soil. When it came time for the demolition, you couldn't move 1 ft. without getting 15 tabs. There was only about 2 or 3 days before they were to fill it in with fill-dirt, so we cranked our disc, and got hundreds of silver coins. Yup, passing nickels. The only other option would've been to pull our hair out digging tabs and foil, when there was simply no way to "get it all", in the short amount of time we had.
So with that said, I respectfully disagree with the addage to "dig all, lest you miss something". It depends on the hunt site, as to whether that's true or not.
