A couple of observations Ive had since only owning the Legend a few months is that it can detect quite deep, whether its a copper penny or a piece of brass or aluminum...like 12 inches or more but youll start losing info at that point and it cant tell you whether its ferrous or non ferrous. That happened to me when I found a small Sterling Silver bracelet, it was very thin but under dense rocky dirt. It ran up at 52 but couldnt tell me anything else. Try to get into the habit of digging everything unless you know for sure its a bottle cap or a pull tab, etc. I call them ghost signals and doubt thats the correct verbage but if you get a strong target ID number with no iron discrimination info, be prepared to dig deep a lot of times. The Multi frequency settings correspond to low frequencies to mid frequencies to high frequencies. The manual says M1 focuses on low conductors but you get better depth where as M3 is aimed at high conductors and their reactiveness. To answer your question Id say Yes, running at 40khz will still respond well to an object 2-3 inches under the ground or under wood chips. Ive had coins lodged under big rocks that the Legend still tattled on but in Multi setting but this is the advantage to using multi simultaneous freq