I actually just tested an 1862 fatty and it is indeed a 12-24. That’s pretty astounding. I had found that coin a couple years ago with the CTX in an old town hall lawn, but didn’t recall it being that low. I guess if you’re somewhere old…gotta dig a lot more of a range to get that kind of thing!
I think you told me as they go deeper, the CO and/or FE change. So I mentally make that adjustment.
I have opened up my CO values a little more to the left to include the Indians. Since I am digging deeper than 4-5" with my CTX I might was well dig Indians. I think they are cool.
I did not have the 1859 and 1862 test so I bought them on Ebay so I could air test them. I guess those are called the Fatties since they weigh more. I am just guessing that at least on these pennies, the differences in weight and compensations account for different TID readings.
I know it is a little arcane knowledge, but I always wondered about pennies and why the rang up different. Of course every one know about zinc memorials and shields.
*********** more corrections ********
Ok, lots of corrections here. I should not have created this chart from the very small print out of "A Guide Book of United States Coins 2019 by R.S. Yeoman, 72nd edition when I had this head cold and taking NyQuil.
Here is the corrected file. I hope I got it right this time, I don't wish to mislead anyone with bad info.
The test was an air test on ground I cleared with my CTX3030 to make sure no other metal items were in the ground. Height was about 7" above the ground using Ferrous-Coin mode. My ground is moderately mineralized but that should not have affected anything since it was an air test.
Sorry for the goofs.