I would watch the vid on the half dollar and look at the screen shot you notice that the cursor has red in it a lot more than the dime or indian because the dime and indian are almost mast out where as the half is not so much mast .
The dime and indian with a smaller nail well have more red than with the bigger screw I used.
As far as 12.40 12.41 showing a cursor on the 12 line and iron in the bottom corner which happens quite often , there well be no red in the cursor and the #s are to high to be located with a coin and nail . The # s that read 12.37 are what I am looking for the reason is this is a blended signal nail with coin no audio any thing higher well give a good signal and will not be silent in my ground 12.40 12.41 are where my falses happen so you will have to see where your #s for falses happen .
The 12.40 and 12.41 are where I get a silent hit I think it has to do with iron rust from a older nails bottle cap or what ever that has decomposed over time leaving just a halo and the machine puts that on the 12 line most of these I have dug I have not found anything there but if you use a magnet you will find rust flakes on it from the hole you dug . So I ignore the 12.40 to 12.41 that are silent because they are rust and anything higher unless it makes a sound .
So 12.37 on the 12 line with red is a shallow coin with a nail or other iron object , ones that have very little red or none at all well be 6 inches or deeper or are just mast heavier than the ones with more red .
Anything lower than 12.37 well be a non ferrous object when it gives no audio but the cursor has red or not . The more red the better .
I would also like to add that anything on the 12 line that reads higher than 12.37 12.38 well likely be iron rust if it does not give audio .
The machine well not give audio on rust but the target trace well show it on the 12 line 12,39 or higher depending on the size of the object that has rusted away . so yes it is a iron false but only to target trace .A audio iron false is a false with a iron object that the machine can see this is a real false as compared to a rust false that shows on the 12 line in target trace . sube