Wanted to link this ID chart thread to a good discussion on where wheats, indians, and zincs, and nickels read for people...
http://www.findmall.com/read.php?21,1774819
And might as well re-post this info I posted there, because I plan to update my ID chart soon with this information on the metal makeup of various years of indians, wheats, copper memorials, and zinc pennies too. I listed a bit of that and the dates in the prior chart posted in this thread, but I'd like to add more to that aspect of it down the road here. I need to update that chart anyway and start trying to compress some of the double listed stuff down. Just wanted to include any conflicting coin IDs from the various charts I found. As I continue to scan in more coins I'll try to compress the listing so it's not as long as it is now. Still, if you shrink it down to print it's about 1 and 1/2 times the length of a pack of smokes so it's not too big of an issue for me to carry in my holster with my digger and Pro Pointer at all times.
Re-Post...
1859 to 1864 indians (88% copper, 12% nickle, which metal detecting circles call a "fatty" Indian due to them being a bit thicker than normal Indians) read 160 to 164. That's right in the pull tab range. The nickle is pulling them down a bit in conductivity, hence the lower VDI reading.
My own readings of 1864 to 1909 Indians (refered to as bronze, which is 95% copper, 5% tin and zinc) read 173 for me, but the other charts list them from there up to 176.
My readings of 1909 to 1958 wheats read 173.
I also scanned some other Indians and wheats that read 176 and 177, but I didn't note their dates in my chart.
I scanned some wheats and copper memeorials that read 179 to 180, but I didn't note the dates on those either.
Zincs usually read 173 or 176, but a few can read between those two numbers or as high as 177 when I've scanned them. Very rare though. For me when digging them they are either 173 or 176 99% of the time. I've dug a few ate up zincs that drop to as low as about 171 or so.
I love digging those odd numbers between 169 (the highest pull tab reading 99% of the time) and 173 for zincs. 170, 171, and 172 are rare for me to come across at sites and often I've dug some cool relics in that number range. They are so rare anyway to come across that I never pass those up, and I keep expecting to dig a bigger gold ring with a high K value, or a smaller one but with a low K value, that can easily read right up in that number range if not higher.
The Sovereign is blessed in that it's 180 meter has super high resolution from foil all the way up to copper penny. Most machines (and I haven't seen one yet that has this high of resolution of the 180 meter in that range???) can't finely separate high reading tabs from zincs, or especially low reading tabs from nickles, but the Sovereign's real high conductivity resolution (from foil to copper penny) can make these kinds of distinctions.
That's why nickels are almost a sure bet on this machine. Around 143 to 146 with a nice round smooth tone and I'll bet money on it being a nickel. Dug a bunch of older ones at pounded out sites just because other machines can't distinctly ID them from tabs, and also the fact that their "nickel" range bleeds lower into more of the foil range too. That's where the old "dig the nickel zone to find gold rings" thing comes from...machines with a much wider nickel zone that are soaking up a wider range of targets a good bit above and below where a nickel will read that they consider a "nickel" ID.
I've dug 4 or 5 war nickels with my GT that read right around a normal nickel of about 144 to 146, but I know some can read higher for people due to the silver content. I've also dug some old Vs or buffalos as low as about 136 or 139 or so, but they still had that nice smooth round sound and the nickel tone to them. But I've dug Vs/buffalos that also were in pretty bad shape and still rang right in the 144 to 146 range like any modern nickel in good shape.
Far as coins above a copper penny, I've owned machines that could ID coin types (or try to anyway), but I've dug a lot of silver on several different machines that could ID coin types that they said were pennies or the clad versions of a dime or quarter but they turned out to be silver ones, so I don't trust that kind of input on what the machine thinks the coin is above copper penny. The differences in conductivity between copper pennies, clad dimes, clad quarters, silver dimes, and silver quarters is such a fine line that anything could throw the ID off (minerals, depth, being masked, on edge, being worn, etc).
For that reason when old coin hunting I don't care what kind of coin the machine thinks it might be. If the coin is deep or it's shallow but mixed in trash, I'm digging it anyway in the hopes of a silver or some other old coin. I've even dug silver dimes that read as low as zinc pennies on machines for all the reasons listed above. High resolution in the coin range also makes the ID a bit "floaty" for my tastes, causing me to question if the target is really a coin or a piece of junk.
In a sense a wider net catches more fish is the way I look at it. I think that's one of the reasons I dug so many old coins with my QXT Pro before my GT too, because the QXT is like the GT in that it has a separate zone for zincs, but copper penny and above get lumped into the same zone.