I went to my trashy, hunted out park to run a little study on the CZ-3D. The site is not, strictly speaking, the kind of site for which the CZ-3D is optimized for. The park did open around 1880 but it has been in continued use since then so although there are still many old coins left, those coins are covered by a carpet of trash.
Nonetheless, I remained undaunted and carried on.
The settings on the CZ-3D were as follows: Discrimination set at zero. Ground Balance at 3.5. Volume at 4.5. Sensitivity at ~4.2. Enhanced mode. Eight inch stock coil.
I detected for two hours and dug only repeatable high tones regardless of the depth of the target. Below are the results
3 memorial cents
5 beaver tails
1 round pull tab with beaver tail attached
2 square pull tabs
2 bottle caps
3 wine screw caps
6 pieces of can slaw
1 bent rusty nail
1 piece of aluminum wire
1 unidentified piece of brass
30 pieces dug
8 good targets
22 trash targets
approx 27% of the targets were good. The oldest coin was a 1959 nickel.
Not bad for a spot of the park that I and others have hit heavily in recent months.
Thank you for looking!