for "city parks", I am usually trying to avoid clad. And the depth-at-which silver & wheaties starts, varies from park to park. Also depending on if you're in hard-pan parts of the (around bases of trees, etc...) oldies could be very shallow. Contrast to lush green grass, where old coins start to be deeper (as a general rule).
That mental criteria cutoff point can be as little as 4" in some parks. Meaning I won't chase it unless it's 4 or 5" or more. In other parks, the criteria could ~7". Because anything shallower than that tends to be clad.
So it just depends on the park. When I arrive at a new park, I test various beeps, to get an idea of sinkage. If I find I'm digging clad dimes at 6", then I'll set my mind to ignore targets 6" or less, etc.....
A person who is angling for park rings, or doesn't mind clad, would have an entirely different answer. Just depends.
