A 1959-D Lincoln cent offered in Heritage’s April 4 to 6 U.S. Coins Signature Auction is an obvious error even to a novice collector’s eyes: It was struck on a silver planchet intended for a Roosevelt dime.

The coin is a form of what is called a “wrong planchet error.” A planchet is the blank disk of metal, featureless except for a slightly raised proto-rim on both sides, used to strike a coin.

So how was this coin struck on a dime planchet made of 90 percent silver and 10 percent copper, instead of on a cent planchet made of 95 percent copper and 5 percent zinc and tin? It has to do with how planchets were transported to coining presses in the mid-20th century.

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Planchets and struck coins were stored in large metal hoppers (or “tote bins”) for transport from one stage to the next stage in the minting process, and these hoppers were not dedicated to any single denomination. A specific hopper could be used to transport dime planchets on one occasion and for cent planchets on the next occasion. This multi-use practice could result in errors of the type offered in the Heritage auction.

These hoppers/tote bins were made of metal and had sloped bottoms to aid in funneling planchets through a side door when opened. Opening the door enabled planchets to be dumped into the feed system for a coining press.

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Sometimes, however, a stray planchet or two could become trapped in a hopper after it was emptied. When the hopper was later filled with planchets again, the trapped planchet could be dislodged and flow out with the rest of the planchets the next time the hopper was emptied.

Trapped with different planchets

This occurrence would not be an issue if the trapped planchet were of the same type as the other planchets in the hopper. However, if the trapped planchet were intended for dime production and the next time the hopper was filled the planchets were intended for cents, then the process for striking a wrong planchet error was set up.

That is probably what happened here. A dime planchet was trapped in a hopper later used for cent planchets, and thus was mixed among these slightly larger and thicker planchets when they were fed into a coining press. This dime planchet was thus fed between cent dies, creating the wrong planchet error. (If a cent planchet had been trapped inside a hopper that was then used for dime planchets, the error would not have occurred. The cent planchet, larger in diameter than dime planchets, would have jammed the feed mechanism for dime planchets and, unaided, would never make it to the dime coining chamber.)

Among error types, cents on dime planchets, while not common, are not especially rare. Both denominations were struck in large numbers in most years, and it is not surprising that a certain quantity of dime planchets would become mixed with cent planchets to be struck as wrong planchet errors.

The coin in the upcoming auction is graded Mint State 64 by Numismatic Guaranty Corp. Heritage states: “.5 grams, identical to the statutory weight of a silver Roosevelt dime. This pearl-white off-metal error is both lustrous and well preserved. Struck aligned with the collar at 3 o'clock, with broad rims near that area and very narrow rims opposite at 9 o'clock. The left-side legends, especially IN GOD WE, exhibit stretching toward the rims. The portrait and Memorial are sharply struck.”

Since the dime is smaller in diameter and thinner than a cent, there is insufficient metal to fill the recesses of the cent dies, so wrong planchet errors of this combination can be somewhat softly struck.

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While the coin in the upcoming auction has no estimate yet, Heritage has sold similar pieces before. A Philadelphia Mint strike of a 1959 Lincoln cent struck on dime planchet, graded Mint State 64 by Professional Coin Grading Service, sold for $1,997.50 in a January 2013 auction, with a 1959-D Lincoln cent on dime planchet graded MS-63 by PCGS sold for $2,115 in the same January 2013 sale.