with lots of possible answers depending on what you are hunting for and where. Here's my take on it from mostly a dig it all perspective
When I am hunting older sites I generally dig everything that is not obviously iron and so dig a fair amount of it in the process.
In that context, other than obvious iron falses, I suppose there really is no such thing as an iffy signal.
Non-ferrous items next to iron are tough, so digging those partially repeatable signals (the ones that repeat only with a "just right" coil sweep) is called for. Call those iffy if you want but they are the prime suspects I look for when hunting in a dig it all mode. There really is no definitive answer as to how iron co-located targets will respond, every one is different. For the dig it all guys, learning how iron responds at low disc settings and going after the rest is the ticket.
A lot depends on the machine and its sweep requirements. Depending on the detector, signals can be best with a broad sweep -- even in iron trashy conditions, some may work best with a tight wiggle over the target and there are some that can do both. At times I may simply go by the quality of the initial hit that drew my attention to the target in the first place. Other times I will work the target a bit before digging if something does not seem quite right but, if it remains questionable it gets dug.
As for the beeps one-way and not the other signals.. please leave them, I'll dig up those goodies later on.
Tom
