Voyager32 the settings i started with but tweak a bit based on the park i am at is. Park2, 40khz, 50 tone, Iron bias 2, recovery speed 4.
This hits loonies and toonies as well as newer quarters. They jump a bit but not as much as bottle caps. I do tend to get about 15-25% more bottlecaps in single frequency but in multi i dont think i have ever dug a loonie or toonie.