If you're looking for coins then "Deep HC" (prog 6) is a good one. Because it uses a lower frequency range than, say, "General (prog 1)" you risk missing out on some smaller items at depth (earring backs, cut quarter/half hammered coins etc.).
Raising Disc to 39 will make things sound quieter, but again, increases the risk that you may miss some smaller and/or masked non-ferrous targets.
Horses for courses, I think.