1) I have never found anything good when digging a weak, pure iron signal that pinpoints in the same location. It has always been a deep small piece of iron. Sometimes it's not much larger than a nail head at 10-12 inches.
2) If you get a loud high repeatable signal, and after you pinpoint, it seems long shaped, not crisp and sharp, lift the coil a foot off the ground. If you still hear it loud, it's probably a can or big iron target. If you're looking for a cache then, DIG!
3) Regarding the bouncing between two different targets: if it bounces from coin to zinc, from what I have seen, it is iron.
4) Iron will usually pinpoint off target.
5) I like to run the discrimination at one. I'll watch the meter as I'm scanning a target, if it bounces from coin to zinc and back it's usually iron. Haven't dug a coin yet that did that but that's not saying it can't be.
6) I have noticed that iron will usually pinpoint off center.
I don't rely on that trait, though, to eliminate the possibility
of it being
a coin. I have found that a coin on edge will also pinpoint off center.
7) I usually set the discrimination at 1, because the iron signals can drive you crazy. However, sometimes I will go to 0-discrimination just as an experiment.
8) Once you have encountered an iron signal that's over 5" deep, hit it from at least 2 angles at 90 degrees apart. If you can get a good tone at these 2 angles AND the signal PINPOINTS IN THE SAME SPOT then DIG! Iron will never pinpoint in the same spot when sweeping the coil at 2 different angles.
9) Dimes and pennies laying flat that are deep will pinpoint very small compared to iron. I've dug a few deep ones on the CZ7 that pinpointed well, sounded good, but bounced back and forth between coin and zinc. That was the tip off and sure enough it was iron.
10) Nails have not been a problem as long as I run at the discrimination at the 0 setting. I've dug a few, but usually they gave low tones in three directions with only a high coin spike in the other direction. It may be because we don't have as much mineralization here as other areas do.
11) The CZ6a takes some getting used to. Find a place that
is not very trashy to learn how to use it. Be patient and slow
down. The 6a will often mis-ID a rusty nail if you sweep it too
fast. When I got my CZ6a, I went to a trashy old park and dug
about 40 lbs of square nails. Since then, I've learned a lot about
the machine's signals, learned to slow down, and be patient.