PART III. Die Installation Errors:

Mismatched Business / Proof Dies

Subtle differences in design details often differentiate dies intended for business strikes and those intended for proof strikes. Cases of mismatched proof and business strike dies (sometimes called Wrong Design errors/varieties) have been plentiful. Cases sometimes appear to be dies seemingly meant for proof coinage, being used mistakenly without proof finishing, used on business class strikes (or vice versa). It has been suggested in some circumstances that proof dies (on ’56-’64 quarters & ’56-’63 halves) after an initial run, could have been used on business strikes to reuse them instead of discarding them (though specific evidence is needed to prove this hypothesis). Whatever the case, they can make for an interesting rarity to keep an eye out for.

Below are the two known reverses for 1998-S & 1999-S proof Lincoln cents, the CAM (on right) is the desirable (rare) version made from a business strike die.

PART II. Die Varieties:

Misplaced Mintmark

Definition: This occurs when a mint mark is placed outside the normal area where a mint mark is found. This event is usually the result of the mintmark punch being inadvertently dropped on the die.

The picture to the left shows a D mintmark punched into the vest area of a 1953 Lincoln cent. There is also another D mintmark to the south of the main mintmark. This picture is courtesy of Brian Ribar.

This 1956-D Lincoln cent shows an unlikely S mintmark to the west of the main mintmark. What makes this unlikely is the fact that no S mintmarks were used on Lincoln cents in 1956. The picture of this die is courtesy of Coppercoins. This is alco considered a dual mintmark. For more information click HERE.

One of the most peculiar repunched mintmarks in the series, this variety shows an extra lower horizontal to the west, an extra lower serif to the northwest, and two completely separated punchings in the vest area.

 The picture of this die is courtesy of Coppercoins.

PART II. Die Varieties:

Other Omitted Design Elements

Definition: Part of a design element, or an entire design element is missing from a working die.

The lower left stem (a continuation of the right wreath branch) is missing on this 1801 United States Large Cent. The image to the left shows the error while the image to the right shows the correct placement of the stem. Also notice that there is a spelling error on UNITED where the U has been replaced by two I’s that have been placed next to each
other.  Furthermore, the denominator of the fractional denomination has the wrong first digit.  A zero has been substituted for the number 1. The images are courtesy of Heritage Auction.

PART V. Planchet Errors:

Rolling / Bonding Mill Errors:

Missing Clad Layers:

Both Clad Layers Missing:

Core Thickness:

Definition: This type error occurs when both clad layers are improperly bonded and peel of the core of the planchet or coin. This error can also occur when the copper core is ganged punched from a strip where the copper core extends past the clad layers.

An undated copper core planchet was fed into the dies along with a normal quarter planchet. The strike adhered the copper core piece to the reverse die. The other coin was ejected, and a new planchet fed in. This cycle repeated until the multi-struck copper core piece stretched to the diameter of a half dollar, and developed edge splits. Copper core pieces are the result of improper bonding between the clad and copper layers, or can be created when the copper layer of the planchet strip extends beyond the two clad layers.

Image and text courtesy of Heritage Auctions.

Part V. Planchet Errors:

Bonding / Bonding Mill Errors:

Missing Clad Errors:

Before Strike:

Before Rolling is Completed:

Full

Definition: During the bonding process, two outer coils of thin clad strip (75% Cu / 25% Ni) are bonded to a middle coil of thick core strip composed of pure copper.  If the leading end of one of the clad strips lags behind the other two strips during insertion into the bonding mill, the leading end of the composite strip will have only two layers instead of three.  Likewise, if one clad strip terminates prematurely at the trailing end of the bonded strip, that trailing end will also only have two layers, one of copper-nickel and one of pure copper.  In each case, the bi-laminar section of strip will be rolled to full thickness.  Any blank punched out of that section of the strip will also weigh the same as a normal coin.

A normal-weight missing clad error will also result when a large gap is present or opens up within one of the clad strips.  This gap will be filled by the copper core during bonding and subsequent rolling.

This is a very rare type of rolling mill error.

This 1976 quarter dollar was struck on a planchet derived from a section of bonded strip that never had one of its clad layers.  It weighs 5.39 grams — 0.28 grams underweight.  A normal missing-before-strike clad error should weigh a full gram less than a normal quarter.  The reason it’s not full weight (5.67g) is that the right side shows a taper.  This is consistent with this blank being derived from an area near the leading or trailing end of the clad strip.

PART V. Planchet Errors:

Bonding / Bonding Mill Errors:

Missing Clad Layer:

Partial:

After Strike

Definition: A portion of the clad layer separates from the coin after the strike.  Exposed design elements are
characteristically mushy.  Loss of the clad layer is due to a failure for this portion of the clad layer to fuse with
the core in the bonding mill.  Inadequate cleaning of the core and clad strip may be responsible.

This 1972-S Proof Eisenhower dollar had part of the clad layer (80% silver, 20% copper) on the reverse face split off after it was struck.

Images are courtesy of Heritage Auctions.

PART V. Planchet Errors:

Bonding / Bonding Mill Errors:

Missing Clad Layer:

Full:

Before Strike

Definition: One clad strip was not properly bonded to the core strip by the bonding mill. This caused the clad to layer separate from the copper core after blanking but before the coin was struck.

This 1977 quarter dollar was struck on a planchet that lost its obverse clad layer after blanking but prior to the strike.  It weighs 4.70 grams in comparison to a normal quarter, which weighs 5.67 grams.

PART V. Planchet Errors:

Improper Alloy Mix

Definition: The term “improper alloy mix” can apply to two related errors.  The constituent metals of a solid-alloy coin can be well-mixed but in the wrong proportions.  In the case of a copper-alloy cent with too much tin or zinc, this will result in a brassy color.  Alternatively, the constituent metals can be in the right proportions but poorly mixed.  This will leave the coin with light and dark bands.  Of course, the two mistakes can occur together. 

The most extreme improper alloy mix errors are those in which the minor metallic element isn’t mixed in at all. This would be a type of “intrinsic metallic inclusion”.

This 1941 cent has a brassy color and consists of 86% copper, 11% zinc, and 3% tin.  A normal copper-alloy cent
of this period is 95% copper, with the remaining 5% tin and zinc.  The component metals are relatively well-mixed.  This coin is also significantly overweight at 3.40 grams.  So it combines an improper alloy mix error with a rolled-thick error.

Light and dark bands on this 1941 cent indicate poorly-mixed constituent metals.  The lighter bands are enriched in zinc, tin, or both.

An unmixed globule of tin or zinc is responsible for the gray band that crosses the obverse face of this 1948 cent.  This is an intrinsic metallic inclusion.

The 1938 (P) Lincoln cent shown above has a poorly blended mixture of copper, tin,  and zinc. This has resulted in mottled bands of discoloration on both the obverse and reverse of the coin.

A poorly mixed alloy can result in alternating light and dark streaks.  This is often referred to as a “wood grain” pattern, and the coins themselves as “woodies”.

The 1908 British half penny  shown above has lamination errors and a poorly mixed alloy. The lighter-colored material seen on both the obverse and reverse of the coin is presumably enriched in tin.  This poor alloy mix may have contributed to the lamination peels.

PART V. Planchet Errors:

Annealing Errors:

Improper Annealing:

Definition: For decades error collectors have puzzled over copper-nickel and Cu-Ni clad coins struck on planchets with a layer of copper on the surface. In times past, these errors were called “copper wash” and “sintered plating” errors. The 1962 nickel shown below is a typical example. It has a thick layer of peeling copper on the right side of the obverse face. The rest of the obverse face and all of the reverse face is black. Copper, red, black, brown, and gray are colors typically found in these errors. Coverage can be complete or incomplete. The copper can range from a slight tinge to a thick coating.

In recent years, eyewitness testimony has convincingly pointed to annealing as the specific step in the planchet preparation responsible for the surface copper. In light of this testimony, these errors are now generally labeled “improper annealing” errors by the major grading services.

In 2010 Mike Diamond contacted US Mint officials with convincing evidence which in the end supported his hypothesis that copper and nickel atoms in the 75% Cu / 25% Ni alloy were migrating and segregating themselves into layers of relative purity. In response to an inquiry first made to Tom Jurkowsky, the Mint’s Director of Public Affairs, an answer came henceforth. Michael White, a spokesman for the Office of Public Affairs, consulted with the Mint’s technical staff who reported a mechanism very similar to the first scenario Mike Diamond laid out. The atoms are migrating to the surface and rearranging themselves into uniform layers. The proximate cause, according to Mr. White, is prolonged exposure to heat, a failure to maintain an oxygen-depleted atmosphere in the annealing oven, or a combination of both. Here is Mr. White’s verbatim explanation:

PART V. Planchet Errors:

Plating Errors:

Incomplete Plating

Definition: This error type occurs when a zinc cent planchet is not fully coated with copper in the plating bath.  The zinc core therefore remains exposed.

It is important to note that exposure of the zinc core prior to the strike can have other causes.  On rare occasions the copper plating peels off before the strike.  Pre-strike damage is another cause.  

The 1995-D Lincoln cent pictured below was struck on a partially plated planchet.

 Images are courtesy of Heritage Auctions.