I am in a gabby mood today so let me see if'n I can hep ya'll out somewhat when dealing with that pesky iron stuff by repeating some of the stuff I have learned from personal experience and from others (especially Monte) on these forums for lo these many years.
Iron stuff like nails and bottlecaps is there, its always going to be there, and you are not going to find a detector that wont audibly react to some of it. And if you do find a machine that is strongly biased against iron, it will also be biased against some other nice targets that are right down there near or in the iron conductance range.
To defeat iron, you must learn to recognize and then ignore it. That probably has more to do with technique than detector design.
First technique....and really important. Keep going down to a smaller coil untill, if possible, you can read each individual target seperately. If the site is so trashy that you have to go down to a 3 to 4 inch coil, so be it, thats the only way you can accurately poke and feel your way around through all the targets and prevent some of the masking effects of iron and other trash.
Second technique....learn to recognize the sound of iron targets using the ALL METAL mode of your detector. But first you need to be hunting with a small enough coil so that you stand a chance of isolating and reading each target individually. Iron targets read as wide as....or wider...than the width of your coil. More conductive targets read less than the width of your coil. With practice you can learn the sound of iron. Your DFX also had a "smeargraph" thingy that showed you a pichur of that long sound by standing up a long row of pips on its graph. You dont need the pips if you learn the sound.
Third technique.....BURN the iffy targets......learn to recognize the sound of iron targets while using the DISCRIMINATION mode. Most iron targets have a sort of "iffy" or "ratty" sound to them, not that nice round sound of a better type target. Roughly pinpoint the target then make a short fast pass over the center of the target with your coil. Thats called BURNING the target. It is most effective if your coil is small enough to isolate the target and your coil sweep is short and fast over only that target. If the sound of the target gets rattier or disappears completely....its iron. If the sound of the target improves in both sound quality and volume...its not iron. It only takes a second and a twitch of the wrist to "burn" a target. If in further doubt, go to the second technique as above, and cross check the targets "width" using the all metal mode.
Fourth technique...dont agonize over the damned iron and learn to cull your targets. You cant stand in one spot waving your coil around and around. If in doubt about the sound of a target, burn it, crosscheck in all metal if necessary, make a decision to dig or not dig and live with the results. Keep moving along with this technique and you can cull the majority of low conductive iron targets while recognizing the better quality low conductive targets.
Choice of Tesoro,s.....I am personally still using an old Golden Sabre II as a coin machine, not a lot of depth but has a beautiful smooth sounding all metal mode with a slow auto-tune that tells me a lot about a targets conductance, size, shape, and depth. I sort of wish I still had the BandidoII Umax that I traded off a few years ago. I think it was the last machine Tesoro made with two all metal modes. It had a selector switch that selected either a true all metal mode without autotuning or a fast autotuned all metal mode. I liked having that choice. There is a tremendous amount of target information in the all metal mode of a detector....providing the detector is designed to have a good smooth all metal mode rather than an overpowered thready winky wonky sounding all metal mode. I haven't used the latest Tesoro units, including the Tejon, but from what I read about them, I kind of think I would prefer my old BIIumax......yep, the one I traded away.
