which is older sites without a lot of aluminum trash. To answer your queestion, try to descriminate out a zinc penny while in the enhanced mode by cranking your descrimination all the way up to 6, I'll bet you it will still hit on the penny. Now flip it to sale mode, it should descriminate out the zinc.
Now, if you get yourself a hand full of nickels and either bury them or pass them in front of the coil, check to see how many of then will register with a hi tone and how many with a mid tone, mine either registered a nickel with a mid tone or a mid to hi tone bounce and registered round pulltab on the meter.
So, when in the field, if I came across a round pulltab signal whether it be mid or hi tone, I would flip to salt mode and if the meter stayed at pulltab, it was mostlikely a pulltab, but if the meter switched to nickel, it mostlikely was a nickel.
Now, the end of this story is, in order to find good targets, you must dig a lot of junk, but if you only dig hi tones like the manual says, you mostlikely are leaving nickels behind.