Lack of copper may not an error: Collector's Clearinghouse
Published: Oct 13, 2015, 3 AM
Since mid-1982, cent planchets have been composed of zinc electroplated with copper. Errors associated with this process include plating that is absent, partial, blistered, cracked, peeling, excessively thick and abnormally thin. Cents struck on unplated zinc planchets are among the most sought-after plating mishaps, in part due to the dramatic color difference.
Unfortunately, unplated Lincoln cents are difficult to authenticate in even the best of circumstances, even for grading services.
Here, then, is a quick tutorial on how to identify genuine unplated cents. I will refer to three examples — a genuine unplated 1989-D Lincoln cent, a 1991-D cent chemically stripped of its copper plating, and a 1994-D cent that was plated-over with a silvery metal.
Seven diagnostics are key to evaluating a suspected unplated cent. Not all are definitive when considered in isolation, so one should consider the totality of the evidence. A genuine example will be characterized by some or all of the following features:
Diagnostic 1. Slightly underweight.
Unplated cents generally weigh between 2.42 grams and 2.48 grams. Our genuine 1989-D cent weighs 2.48 grams. The normal average is 2.50 grams.
Reduced weight is only a start, because a de-plated cent will also be underweight to the same degree. For example, our 1991-D cent weighs 2.47 grams.
As with any denomination, cent weights will vary, with some falling above or below the mean. It’s therefore possible to encounter a genuine unplated cent that matches or exceeds the weight of a normal cent.
Cents that have been plated-over are usually slightly overweight. However, our over-plated 1994-D cent weighs 2.5 grams — the same as a normal cent. I suspect that the host coin was originally underweight, with the added metal raising it to the standard value. While this was probably an accidental choice by the vandal, I wouldn’t put it past a crafty individual to weigh a large number of normal cents, set aside those that are slightly underweight, plate them with zinc, and still have a cent that’s slightly underweight.
Diagnostic 2. Smooth surface.
This criterion cannot be used to distinguish genuine unplated cents from over-plated cents. But a rough surface that is either pitted or studded with microscopic bumps will indicate that the copper plating was chemically stripped. Our de-plated 1991-D cent has a rough surface studded with innumerable tiny bumps.
One proviso: A clever individual can chemically strip the copper plating and then re-plate the coin with zinc in order to hide any microscopic imperfections.
Diagnostic 3. Presence of original Mint luster.
The surface should be bright, but not excessively so. This is true of our genuine 1989-D cent. A brilliant sheen — like that seen in our 1994-D cent — is a reliable indicator that a cent has been plated-over. By the same token, a dull, leaden surface luster will also often indicate a layer of added metal, such as mercury or lead.
Reliance on original Mint luster becomes problematical if the coin has oxidized. A powdery surface that ranges from dark gray to light gray can reflect oxidation or de-plating (or oxidation following de-plating). In any event, a coin with this kind of surface appearance must be assessed with other criteria. Or you can avoid the effort entirely by steering clear of any alleged unplated cent (raw or slabbed) that lacks Mint luster.
Diagnostic 4. Fine streaks on one or both faces.
The fine streaks seen on unplated blanks and planchets are often not completely erased by the strike. The 1989-D cent shows these streaks on both faces. Since their presence is variable, the absence of streaks cannot, by itself, be considered a disqualifying feature.
Diagnostic 5. No microscopic flecks of copper.
If your specimen does show copper flecks, it was almost certainly de-plated.
Diagnostic 6. A clear die-struck design.
Both de-plating and over-plating will tend to soften the design. However, die wear will also soften the design, so this criterion is not always reliable.
Diagnostic 7. No blisters or surface undulations.
The presence of such topographical irregularities indicates that there’s a normal layer of copper plating beneath an applied layer of silver, zinc, tin, nickel, chromium, mercury, lead, cadmium, or “pot metal.”
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