The Lincoln cents from 1982 on, are a zinc base metal with a very thin copper wash. They usually read 06/07 -- 25/27. Depending on the degree of corrosion/soil/depth. The early Indian heads from 1859-1864 were 88% copper & 12% nickel. These will read somewhere around a nickel reading. I will get a 08-06 all the way up to a 15-07 on nickels. It also depends on corrosion/soil/depth. Starting about halfway through 1864 to 1909 the IH's were 95% copper and 5% tin+zinc. these are the IH's that will read like a modern zinc based penny. Here is what I do.....if I'm on an older property that has even a small chance of IH's on it, I will dig any penny type signal...especially the iffy ones. Of course this also applies to any coin type signals. Remember.....nearby trash, moisture, depth, mineralization, corrosion, coin position, and machine settings, can alter a good coin signal, into a very trashy sounding/iffy signal. It takes a lot of digging experience, to tell the difference. That's why the minelab veterans on this forum find so much good stuff, where others have failed. It's not that their machines are that superior....although the Explorer does have some advantages, it's that they know how to really interpret those trashy/iffy signals. I personally think that the Explorer users in general, are the most dedicated to learning their machines, and pushing the envelope to the max....They truly understand what their machines are telling them. Heck....anybody can cherry pick a site. But only the REAL coinshooters with Explorers can nearly clean it out. Oh yeah.....about those IH's sounding like the zinc pennies.....I know of several IH's that were less than an inch deep in the ground. So you can't always rely on judging a good target by the depth. My best IH was down less than 2 inches in with a V nickel. I got a iffy 05-20 on the target display but a very good audio, so I dug it. 1893 IH and a 1911 V nickel. Ya just never know where those good targets might turn up...