I've already been PMing u2robert about his question but I thought it good to go ahead and put that info in his topic.
With the bad coil on mine when it acted up (which was most of the time) coins fell LOW! quarters came in more around dimes,
Dimes and copper pennies fell more towards Zinc's,
Nickles fell to either high iron or foil.
And at that time I had iron disc out,
I had foil disc out (No nickles)
Zinc's were disc out (no copper pennies or dimes) That was a real head scratcher, knowing I had nickles and regular pennies and dime in my test garden but the detector wouldn't hit them.
And when the coil acted up it also was VERY unstable, you could hold the coil up in the air and the numbers on the display was l over the place and a lot of falsing. You could lower the sensitivity a LOT! and set the threshold to a MUCH higher minus number and help the falsing some, but the coin ID was still off. The replacement coil fix all the problems, its now stable even at higher sensitivity and threshold settings. I can run the sensitivity to 8 and the threshold to minus 5 most everywhere.
Hopes this helps.
Mark