Why do Indian Head pennies read differently?

[gary s fl]

Variety 3 (1864-1909) IH pennies read lower and/or disc out lower than wheat & memorial cents on most if not all detectors. The Var. 3 IH and Lincoln wheat cent have the same composition (.950 copper, .050 tin & zinc), weigh the same (3.11 grams), and have the same 19 mm diameter. Anyone know why? HH

 

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[Tom_in_CA]

Good question. You'd think they would/should read exactly the same @ TID. Maybe the answer is the same as the reason why wheaties from the teens have a slightly different TID than wheaties from, say, the 50s. Ever noticed how the earlier wheaties read a tad lower? And it has nothing to do with time spent in the ground, because you can test non-dug ones, and you'll see the TID difference. Yes, it's only a tad different (only noticeable on scales, like the Whites XLT which has like a 100 pt. scale). I've heard that the reason is that the copper that went into the various years coins, came from different mines/states. Like for example: in the teens, maybe Uncle Sam buys all their copper from Idaho mines. But starting in the '20s sometime, switches and is buying their copper from mines in Montana, from different mountain ranges.

There is differing impurities in various metals, depending on where it is mined. For example: in gold, you can have various shades of yellow, to orange ("rose gold") depending on where it was mined from. Those subtle impurities affect the TID supposedly. This might explain a *slight* TID change, but the big change of TIDs from IH's to wheaties, seems to be a stretch for that explanation.

 

[Sandman]

I suspect the IH have been in the ground longer and lost some of their conductivity. I noticed this too.

 

[Tom_in_CA]

Sandman, the time spent in the ground is not the explanation. The TID difference can even be seen on non-dug coins. Like, if you were to get a common non-dug IH from a coin store, it would read the same, despite never having been in the ground, non-worn, etc....

Yes, the TID can drop even lower after 100 yrs. in the ground (true for wheaties too), but the starting TID, fresh from the mint, is different between IH's and wheats.

 

[gary s fl]

Tom, thanks for the reply. The different copper mining locations and impurities may have some validity but like you said it seems like the range difference is too great to account for that only. As for the different colors of a similar karat gold, I think that has more to do with what the composition of the other metals were ie, copper, nickel, etc..

Sandman, I thought about what effects corrosion may have but even cleaned IH's read differently. It may be a combination of several things. It's just that all IH's out of the ground that I've found read lower wheats. Thanks.

Tom, your too fast.

 

[EasyMoney]

That is a very good question, isn't it?

Metal detectors read the electrical conductivity of targets, plus size, thickness, and another very interesting things too, that being that oxidized conductors will not conduct electricity as well as clean metals. However, that doesn't explain why some pennies read lower or high in the air just like they do in the ground, but they do. If a field is disturbed (because of corrosion) the path is no longer "balanced" as in two-way signals in this case and that can be read as interference, even with RF, FM, AM, pulse, and static electricity.

I have noticed that some pennies are a bit thicker than other pennies too, and sometimes by quite a bit. Maybe they are just plain worn thin too, but I wouldn't think it would be enough to change any reading much, at least not by itself.

BTW, "rose gold" is gold with copper mixed into the gold (smelted together), and that's why it apears pink. I found a rose gold signature ring once with no initials on it yet. It was .75 gold (24 Kt), and I finally sold the thing because too many people were interested in getting it from me. It weighed more than 3/4 of an ounce and I got some really good money for it, in fact, the same price of pure gold at 3/4 ounce.

It must be that the combination of thickness combined with the good or bad conductivity of the copper that makes the difference in it's conductivity read by a metal detector. Nothing else really makes much sense.

 

[stoney56]

Maybe I'm just shooting in the dark but I've noticed that IH's around here tend to have a bit more oxidation than even early wheats. Maybe the oxidation is interfering with the true signal. The same goes for lead--sinkers seem to TID higher than say 3 ringers.

 

[Farmercal]

Perhaps it is the shape and when I say shape I mean design. The design or art work of the indian is different than that of Lincoln and perhaps that different shape gives the different read on the detector. Just a thought.

 

[gary s fl]

All these theories may be valid. Since I don't own a non-dug IH I'm going on Tom's post that even a non-dug IH and wheat TID different, so corrosion probably has a minimal effect. The design, shape of the rim/lip, and possibly even more, the amount of stamped relief may contribute more to the difference. The lettering, date, oak wreath, and portrait look bolder on IHs compared to wheats and memorial cents. I'm going to ask the same question on a technical forum. Thanks for the input.