Great chart!
The reading use air for the test but since most coins are of alloys, then silver and gold the metals are stable enough that the reading are not that far off from the actual ones for coins in the soil. The less stable metal such as lead in a mini ball will read 8/22 for an air test but about 13/22 or so in the soil.
The readings for the Smart screen indicate any reading from -6/31 can be coins or jewelry. However the digital display does not indicate a negative number. The reason why is the horizontal axis is actually the metals inductance which is in large part a results of the ferrous content of the metal. The scale is from left to right with zero at the far right and thirty one at the far left. A -6 on the Smart screen is a digital reading of ferrous 22. So any ferrous reading of 0 through 22 should be looked at pretty close. In addition FE coins will have a ferrous reading in the high ferrous of about 31 as will some Indian Heads. Some Indian Heads have a reading that jumps between 31 ferrous and 31 conductivity.
Again, I have attached an illustration.
HH, Cody
