Wow, nice finds! Glad you enjoyed that little field guide. You might want to look in this forum for a thread a month or two back where I posted more tips for the QXT that weren't covered in that the guide. Mainly I cover how to tell various coins from each other but also include a few other tips that were not in it. Originaly I had planned to do a book for the machine since nobody seems to know much about it but decided not to. I do have most of that wrote and may just complete it and throw it up for free in the near future. Please, no emails about it. If and when I finish the thing I'll post a notice. Again, glad you enjoyed it.
Those who know how to set up and run the QXT properly will find it does things no other machine can. It's also a very deep coin shooter provided you set it up the right way and swing fast/short over deeper targets once you find them. Deep coins might at first only sound off as a ground or iron signal, so I prefer to keep those zones accepted as well. This way if you hit a deep/soft low tone you can try the fast/short sweep to try to pull a better ID out of it. Doing this will get you deeper than the vast majority of machines on the market using the same size coil. It's low frequency combined with a few unique features hits hard on deep silver and copper coins.
Gold ring hunting is a little more tricky due to the lack of VDI numbers to avoid trash but it is possible to split hairs on trash when looking for rings. I've found that most gold rings will bounce evenly between the foil and nickle zone on the VDI display as you sweep over them. Very large gold man's rings may make it up into the roundtab zone, but most I've tested were jumping from foil to nickle. Always dig these if they are round, smooth, warm, soft sounding, ring sized targets. Foil and other trash will tend to be scratchy, break up, sound harsh or tinny, or bounce around to other zones more. The QXT's audio only has 3 types- high, low, & all metal when in mixed mode, but I prefer not to use mixed mode (disc. goes just as deep as all metal on a QXT). I just assign high/low tones to the targets I'm looking for. It's deadly in trash using no discrimination and just listening for a high mixed in. It has such a quick recovery speed even with the 9.5" coil that I find it seperates better than other machines using 5 or 6" coil.
The M6 looks like a winner to me for coin/ring hunting. It has four things I wanted on a QXT- VDI numbers, variable discrimination, more tones, and larger coils to max out depth. The three things I don't like about it are it's higher frequency (better on gold but not my top choice for silver/copper coins), it's lack of a notch, and no noise reduction OFF function which helps the QXT to punch even deeper. In some situations I find I'd rather notch out a certain zone of targets than try to ignore hearing them. That's one powerful feature on the QXT- 8 notch zones. The selection of large coils for the M6 to max out coin depths should make up for any lost depth on coins caused by the higher frequency, but I still want to compare it. I'll be picking up an M6 soon to do further comparisons with, depth being one of them. Even if it isn't getting QXT depth on coins with a larger coil (think it will though) it'll still make a very good ring machine in the trash with it's VDI numbers.
It's a little worn but in perfect working order. Had to make room for an M6 in my line up to try for a while.