Excessive heat, edge damage transform anomalous planchet

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Published : 09/14/13
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Several previous columns (Feb. 13, 2012; April 22, 2013) have dealt with Jefferson 5-cent coins struck on underweight, full-diameter (or nearly full-diameter) copper-nickel clad planchets.

Those coins struck on quarter dollar stock pose no conceptual difficulties. Others appear to have been misidentified and are most likely underweight, improperly annealed planchets that started out as solid copper-nickel discs. Still others, like the 1994-P 5-cent coin reported in the first article referenced, are difficult to categorize.

Error dealer Fred Weinberg has provided what is likely the earliest example of such an error, a 1971-D Jefferson 5-cent coin encapsulated by Numismatic Guaranty Corp. and tagged with the understated label “struck on a clad planchet.” On both faces, gaps in the presumed clad layers reveal interior metal that is rusty red and uniformly grainy (see photos). The color and microscopic texture of the interior metal are strongly reminiscent of planchets that have been exposed to excessive heat in the annealing oven.

Improper annealing also causes the copper and nickel fractions of solid copper-nickel planchets and copper-nickel clad layers to migrate and segregate out into relatively uniform layers and patches, with copper often migrating to the surface. Therefore an improper annealing error neither confirms nor falsifies the proposition that the 1971-D 5-cent coin was struck on a nonstandard clad planchet. It simply complicates the picture.

The picture is further complicated by circumferential edge damage prior to the strike. The edge was rolled and squeezed, with metal relocated from the edge to the perimeter of both faces in the form of a thin, narrow apron. Each apron was subsequently struck into the coin with the internal margin currently demarcated by a fissure. Similar damage has been identified in off-metal errors and coins struck on their proper planchets (Nov. 15, 2010; Jan. 23, 2012). The apron appears to overlie the exposed red metal of the 1971-D 5-cent coin, suggesting that the damage occurred after annealing. The 1994-P 5-cent piece referred to earlier appears to have less severe damage of a similar nature.

The edge of the 1971-D 5-cent coin is a uniform brown, with flecks of nickel-colored metal. The 1994-P coin has a uniform copper edge. Both coins therefore lack the incomplete, asymmetrical exposure of the copper core that is seen in normal copper-nickel clad planchets.

Asymmetrical exposure results from the bottom clad layer of the coin metal strip being dragged over the edge of the blank as the latter is forced through a hole in a perforated base plate by the blanking die. Absence of smeared cladding can easily be accounted for by the edge damage. Even normal dimes and quarter dollars that have had their edges rolled and squeezed outside the Mint show an all-copper edge.

At the same time, it’s impossible to eliminate the possibility that the edge was like this before the damage or is a consequence of improper annealing.

NGC reported a weight of 3.2 grams for the 1971-D 5-cent coin. Seeking verification, I cracked the coin out and obtained a more precise weight of 3.18 grams. It just so happens that the expected weight of a 5-cent coin struck on copper-nickel clad dime stock is 3.19 grams. However, since some surface metal is missing and because the edge damage could have subtracted additional mass, the original weight was certainly higher.

If the original weight did exceed the expected range of variation for 5-cent blanks punched out of dime stock, then perhaps the source was rolled-thick dime stock. While this might sound like special pleading, there is a precedent in the form of a 1971-D Washington quarter dollar struck on rolled-thin, silver-clad, half dollar stock (see previous references).

Error dealer James Essence has bolstered the case for a nonstandard clad planchet with a 1983-D Jefferson 5-cent coin that was struck on a defective, improperly annealed dime planchet that shares many similarities with the 1971-D 5-cent piece. Narrow gaps in the cladding expose reddish-brown metal, while flaking along the perimeter has exposed a grainy interior. The edge is also 100 percent copper.

The totality of the evidence suggests that the 1971-D 5-cent coin was indeed struck on a copper-nickel clad planchet and that it is probably dime stock (and unique in that regard). I have yet to encounter an improper annealing error on a solid-alloy planchet in which every gap in the surface metal reveals underlying copper.

Coin World’s Collectors’ Clearinghouse department does not accept coins or other items for examination without prior permission from News Editor William T. Gibbs. Materials sent to Clearinghouse without prior permission will be returned unexamined. Please address all Clearinghouse inquiries to cweditor@coinworld.com or to 800-673-8311, Ext. 172.

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