Rob keep preaching to these guys about the Spectrograph. I have been really concentrating on the Spectrograph and the last few Nickels I dug ID 19 but so does a figure 8 tab. My Spectrograph developes a funny inverted T on the bottom bar when it is a Nickel and it doesn't do it on a tab. I have been using the little 4X6 coil and liked it so much I bought a 6X10.