Valuable vs. Other Forms of Doubling

Many collectors interested in valuable “doubled dies” and “repunched mint marks” (RPMs), have trouble distinguishing them from other forms of doubling. This includes several forms not considered particularly collectible or valuable. Many are “mechanical” in nature and originate during the striking or ejection of the coin from the press, while others are the result of die deterioration. While the collectible forms of “die doubling” are created due to misalignments of multiple images being impressed into a die, the less desirable forms of doubling actually have their origins in the erosion or alteration of existing design and really have nothing to do with distinct die variety or an errant die being produced. The descriptions and images below should aid in your understanding of these differences.

Doubled Dies

(Extremely Collectible)

Hub doubled dies (commonly referred to as “doubled dies”), are the result of the hubbing process. A hub is a master tool made in hardened steel that contains an exact image of a coin. It is used to impress its design into working dies that are then used to strike coins. Hub doubling is possible on many world coins due to a phenomenon known as work hardening, which causes the metal of the face of a die to become too hard and brittle to allow a complete image to be sunk into a die in one operation.

Several impressions or hubbings were required to produce a die using the old multiple hubbing process. Between each hubbing the die was removed from the press and annealed (softened), thus allowing for another impression without shattering the die. This process was repeated until a satisfactory image was achieved. If a misalignment of images occured due to improper indexing during the reinstallation of a partially finished die into a hubbing press for a subsequent impression, a doubled die resulted.

In recent years, the multiple hubbing process has been replaced by the United States Mint by the more modern “single squeeze” restrained hubbing process, which was supposed to eliminate hub doubling on coins, starting in 1997 for the cent and five-cent coins and the balance of most denominations in 1998. However, since the time of the first edition of this book, this has proven to be untrue and many doubled dies have been created from a different set of conditions (die/hub slippage during the initial hubbing). Doubling in more centralized areas of design now predominate and has resulted in hundreds of doubled dies now known on modern coins, with the very best ones added to this third edition.

Doubled dies have proven extremely popular with collectors and often command very significant premiums over the normal value of the coin.

Repunched Mintmarks

(Extremely Collectible)

Up until 1990, all mintmarks were punched into otherwise completed regular coinage dies individually with a hand punch and mallet. This process allowed for variations in the placement of the mintmark, variations in its strength, and sometimes whether it went into the die at an angle or perfectly flush with the field, or tilted clockwise or counterclockwise. It often required several taps of the mallet to sufficiently sink the mintmark into a die. At times, a punch appears to have been angled too far in one direction, creating weakness at one side and strength at the other. This was compensated with a correction that angled later taps of the punch in the direction of weakness. Other times, the engraver probably examined his work and decided it needed strengthening and thus set the punch back down for another blow. Still other times, a first impression of a mintmark was up too high, encroaching into the date, or far too low, or perhaps even rotated at an unacceptable angle that could be as severe as 180 degrees (resulting in an inverted mintmark)! These factors, and plain old-fashioned “punch bounce,” are all conditions that are known to have caused repunched mintmarks (RPMs).

The diagnostics of RPMs, and other forms of repunching not covered in this book, are identical to that of doubled dies; there will be separation lines between overlapping images and lots of total separation in the form of “split serifs.”

Strike Doubling

(Non-collectible)

Most often, doubled dies and RPMs will show as overlapping images that are rounded and in relief with some degree of separation between images. “Strike doubling” appears as a shelf-like extension next to the affected design(s). This effect is illustrated on the date and mintmark of the 1969-S Lincoln cent shown on the next page. This form of “strike doubling” is the result of “die bounce” that may occur within a split second after the strike. Note that there is no separation of design and that the original raised portions of the date and the mintmark have been smashed or pushed into the field resulting in the flat shelf-like appearance. On uncirculated coins, the shelf often has a shiny appearance identical to what you’d see on a fresh scrape. This is because the original Mint luster was destroyed by the scraping of the die on the design when the shelf was created. Compare this coin to the genuine 1969-S doubled die cent in the Lincoln Cent Variety listings.

“Strike doubling” is often referred to by others as: “machine doubling damage,” “mechanical doubling,” “chatter,” “die bounce,” and a host of other terms. They all refer to the same basic type of doubling. It is very common on many dates of U.S. coins and is not considered particularly collectible by most specialists. We assign no extra value to this type and consider it a form of damage on the coin because it occurs after the coin was struck.

Strike doubling shown on the date of a 1969-S Lincoln cent.

The 1971 doubled die cent shown below is a superb example of “hub doubling” or what is commonly referred to as a “doubled die.” Notice that you are looking at overlapping images with some areas of the word LIBERTY showing total separation between individual letters. The doubling is well rounded and exhibits Mint luster on both the primary and secondary images.

Here is another example of strike doubling on a 1968-S Lincoln cent. Notice that there is no separation of design and that the secondary image is flat and shelf-like in appearance. Also note, that unlike doubled dies, the remnants of what is left of the original raised undisturbed portions of the date are now narrower than normal since parts of it have been flattened down into the shelf.

Strike doubling shown on a 1968-S Lincoln cent.

Flat Field Strike Doubling

(Low Interest Collectible)

Another form of “strike doubling” that occurs on coins is what we refer to as “Flat Field Strike Doubling” (FFSD). The most frequent cause occurs when the upper “hammer die” slams down on a coinage blank (known as a planchet) and imparts a light partial image on the planchet a split second before the ram bottoms out and applies the pressure required to form the complete image on the coin. If there is any “slop” in the press in the form of loose die bolts, etc., then a slight slippage can occur between the first impact of the die with the planchet and the impact of the ram exerting the primary force necessary to strike the coin. This may cause doubling of some or all the images on the coin. It is characterized by a shelf of doubling that is clearly outlined but struck flat with the field of the coin. Since these minor images caused by the initial kiss of the die are essentially “restruck” by the dies, when the pressure is applied by the ram, they will show Mint luster and have no effect on the primary image that can be of normal diameter.

However, due to the slop in the press, “Flat Field Strike Doubling” is often found in combination with the more common form of strike doubling described previously. Shown is a look at LIB of LIBERTY found on a 1970-S Lincoln cent that displays a good example of FFSD.

Flat field strike doubling on a 1970-S Lincoln cent.

Since FFSD occurs within the minting process, it technically is a legitimate mint error. However, few collectors or even researchers understand it, and it is often mis-diagnosed as regular “strike doubling” and assessed as a “damaged coin” rather than an error. Few collectors have expressed an interest in this error type and as such we assign no extra value to it except for the most extreme examples on proof coins.

Ejection Doubling

(Non-collectible)

Another form of strike doubling that occurs to coins is known as “ejection doubling.” It occurs when a coin sticks to a lower die and is virtually ripped off the die during its ejection from the press by the feeder/ejector fingers or other ejection systems. The doubling will show as a raised knife-like burr on the effected design elements. Here we show the reverse of a 1959 Lincoln cent showing “ejection doubling” on the lettering of STATES OF and E PLURIBUS UNUM.

Because this form of doubling occurs after the coin is struck, it is considered a form of damage to which we assign no extra value.

Ejection doubling on a 1959 Lincoln cent.

Die Deterioration Doubling

(Very Low Interest)

Another very common form of doubling found on coins is “die deterioration doubling,” (DDD). It is the result of die wear or improper heat treating (of the dies) combined with die wear. The effects manifest themselves as doubling, thickening, twisting and other deformities usually most pronounced on lettering or other designs closest to the rim and progressing inward on extreme examples. It is often found in combination with heavy die flow lines or irregular fields often referred to as the “orange peel fields.” DDD takes on a variety of looks depending on the geometry of the design, metals being struck, pressures used, and other factors. This makes it difficult to illustrate exactly what it might look like on every coin. However, we show several examples to give you some idea of its general characteristics.

Bear in mind that DDD is most common during years of high coinage output when the Mints are forced to extend the use of dies to their extreme limits. Although DDD can be found on almost any date, it is very common on the “steel cents” of 1943 (where it can be extremely pronounced), on other Lincoln cents starting in the 1950s, and on Jefferson nickels and Washington quarters starting in 1965, thus becoming almost epidemic on the nickels since the early 1960s and on be affected a bit less due to less demand to strike them.

Die deterioration doubling.

Due to world record coinage output of the state commemorative quarters, DDD has been exceedingly common on these issues and is expected to continue to be so.

Shown above are examples of DDD on the obverse of a 1993-P Washington quarter (on the P mintmark and on IN GOD WE TRUST) and on the reverse lettering of a 1983-D Jefferson nickel.

DDD is a legitimate die variation but is inherently dynamic, so much so that it is impossible to catalog it by stages. It is also considered by most as a “normal” part of die-use and nothing out of the ordinary. For these reasons, and because it is extremely common, nobody catalogs it and very few knowledgeable die variety specialists bother to collect it. We assign no extra value to this form of doubling on U.S. coins.

In contrast, we show a hub doubled die on IN GOD WE TRUST on a 1946 Roosevelt dime. Compare this doubling to the doubling on the 1993-P Washington quarter shown previously. Notice the overlap of images and strong separation lines on the doubled die.

Hub doubled die on a 1946 Roosevelt dime.

Plating Split Doubling

(Non-collectible)

Lincoln cents struck since mid-1982 are comprised of a thin layer of copper plating bonded to a solid core of zinc. This plating can be stretched so thin during the striking of a coin that it may fracture around the boundaries of certain designs — in particular those that are at a sharp angle to the field like the mintmark. When such fractures occur, not only do they expose a narrow band of zinc but a thin section of plating often snaps back and creates a ridge-like pile-up that is slightly raised and can look similar to the remnant of a weak Denver mintmark (when it occurs next to the D). It may also occur around other designs, (such as IN GOD WE TRUST), but is often less pronounced since the balance of designs are hubbed into the die and are usually more rounded to the field.

Plating split doubling is a very minor defect and inherent to the process. We add no extra value to this variation.

Shown below are three different mintmarks exhibiting plating split doubling.

Plate split doubling adds no value to a coin.

Plating Blisters

(Non-collectible)

Plating blisters may occur in isolated areas or all over the surfaces of a copper-plated zinc cent. The blisters are most often the result of a condition known as “foaming,” associated with the use of contaminated electrolyte used to facilitate the electroplating of the cent blanks. Other organic pollutants affecting the plating or zinc oxidation may also be factors.

These blisters take on numerous shapes and sizes and when shaped “just right” and located next to a mintmark, may be confused with an RPM.

Shown is a photo of a 1982-D with a plating blister mimicking an RPM. Plating blisters, though often tolerated by collectors, are considered less than desirable, and we assign no extra value to them.

Plating blister on a 1982-D Lincoln cent.

1990 Lincoln Cent

The exact cause of this “dot” is unknown, but believed to be “in the die” and therefore reproducible. It is doubtful to catch on as a highly collected variety, but it is a neat find that you can add to your collection of varieties pulled from pocket change. Photo courtesy John A. Wexler.

Die Trails & Wavy Steps

(Low to medium collecting interest)

Die Trails are thought to occur secondary to movement of the die during the hubbing process. They can appear as light “trails” of the design elements and often called “wavy steps” or “wafffled steps” on Lincoln cents. These “trails” can be found on nearly any denomination, but are prevalent on Lincoln cent from the mid-’80s to now. These types of varieties do NOT bring large premiums, but they are fun to find and prove that you have an eye to spot abnormalities. The interest level in these is not high, so don’t expect to make a fortune, but some of the stronger trails could bring a few dollars.