The lack of Iron Audio Volume on the Fors Core is the only thing holding it back from getting a "its perfect" certification sticker but other than that on the machines I have that offer Iron Audio volume ( and machines that don't) I still set them up the same way I was taught.

I set them up to just barely accept iron nails and listen to it all. That way it gives the machine the best chance to unmask a coin out in all that junk. Turn the iron volume down low, but just enough to just hear it so you have an idea of how much iron etc you are dealing with. But that is with a machine that does " Iron Audio Volume " correctly.

CoRe,Relic & Racers
MXT All Pro & M6
Big Red 440