The 9 Classes of Doubled Dies

The direction on all hub doubling is determined by which hubbing is weakest and less complete towards the hubbing that is clearest and most complete. Note: RPMs are the opposite.

Class 1 (I) Rotated Hub Doubling:
When one thinks about a doubled die, Class 1 probably is the type that one imagines as many of the big classic doubled die examples through the years like 1955 1c DDO-001 where indeed Class 1. The misalignment in this type of hub doubling emerges from two separate hubbings. Prior to the second hubbing, the working hub or the working die becomes rotated relative to the original (or first) hubbing. Class I doubled dies are identified as displaying a clockwise (CW) or counter-clockwise (CCW) rotation.

Doubling typically has a rounded appearance. When the hubbing impressions are extremely close, the doubled die may only be recognizable from notched serifs and corners, subtle separation lines, or extra thickness. Other big examples include 1972 1c DDO-001; 1969S 1c DDO-001; 1934 25c DDO-001

Class 2 (II) Distorted Hub Doubling:
The next class, class II, is harder to find empirical evidence to conclusively prove the cause of the hub doubling. Most often hypothesized as a misalignment event relating to either the die or the hub, which has expanded or contracted too much in relation to the first hubbing during the annealing or tempering processes. Class II is characterized by having a spread along the outside devices from deepest to lightest hubbings, which goes toward the Center (C) or towards the Edge (E).

Dies are annealed (cooled slowly) to make them softer so they are more susceptible to taking an impression of the hub. The hub in contrast is tempered, quickly cooled, so that it is more durable and does not distort while transferring an image to the die. If for whatever reason, either the die or the hub did not to return to normal size in between hubbings, doubling would be more pronounced toward the rims. Most examples go toward the edge. 1971 proved to seminal year for Class 2 doubled dies. Classic examples include 1971 1c DDO-001; 1964 1c DDR-020 and 1971 5c DDO-001.


Class 3 (III) Design Hub Doubling:
One of the easier doubled dies to explain, yet the least common to have occurred. Class III Doubled Dies arise when, after the first hubbing with one design, another hubbing follows of a different design, or a slightly altered design. Such differing design mix-ups could come from an intentional alteration during the year, designs from adjacent years, or from hubs intended for proofs mixed with business class hubs.

Many involve the date such as so-called large dates and small dates being hubbed one over the other. Examples include 1960D 1c DDO-001; and 1970S 1c DDO-003.

Note: all doubled dies involving overdates after 1909 are from a hub from one year hubbed over or under that of the next or previous year’s hub inadvertently. Examples include 1942/41 10c DDO-001; and 1943/42 5c DDO-003.

Class 4 (IV) Offset Hub Doubling:
The misalignment event involved with this class of doubled die occurs when two hubbings have their centers misaligned directionally as opposed to rotationally. It is characterized as having doubling that is evenly spread in one direction. The doubling is unlike that found on Classes 1 or 5, where the misalignment-event shows a rotation at or near the center (class 1) or at or near the rim (class 5). Doubling is often rounded, found closer to the center, and when identified on numeric or alphabetic characters it will show notching.

Some examples are hemispherical and may involve tilt making them a hybrid Class 4 + 8. It is also possible, if not common, to have at least a small amount of rotation, see 1984 1c DDO-001.

It has been hypothesized that the reason many examples do not show doubling near the rim is because one of the hubbings only received an uncharacteristically incomplete hubbing. Such an incomplete hubbing would result in design elements not being pressed deep enough in the middle of the die, and not at all along the perimeter. The die originates in a conical shape until it is completely pressed down, if the incomplete hubbing was the first, the outer devices may not have been hubbed the first time around. Conversely, if the offset hubbing was second it would have to be incomplete for whatever reason.


Class 5 (V) Pivoted Hub Doubling:
Class 5 doubled dies are related to Class 1 doubled dies as they both have a misalignment even that involves rotation. If one understands Class 1, rotated hub doubling, then understanding pivoted hub doubling will be easier. Where pivoted hub doubling differs is that the point of rotation is very near or at the rim. (While rotated hub doubling may not always be dead center, nevertheless, as long as it is in the central area, it is considered Class 1 whereas anything near the rim is Class 5.) Classic examples include 1995 1c DDO-001; and 1995D 1c DDO-003. 

Like rotated hub doubling, doubling is either Clockwise (CW) or Counter-clockwise (CCW). Unlike rotated hub doubling, the degree of rotation (or the spread) is strongest opposite the pivot point. Doubling progressively diminishes from there as you move toward the pivot point. Rotated hub doubling, by contrast, shows the same degree of rotation all away around. On some mid-20th century examples, it is not uncommon to have a hybrid Class 2 + 5.


Class 6 (VI) Distended Hub Doubling:
Distended hub doubling is related to a sideways (lateral) expansion that occurs during the hubbing process causing a unique misalignment event. The expansion of the die face is hindered in areas where raised elements on the face of the working hub interlock with the newly or previously penetrated die face. The lateral expansion causes distortion in elements that are relatively near the periphery of the die face as the die expands around stationary elements of the hub creating an expanded void laterally. The affected elements can be thickened, and may show sloping, pointing, or twisted regions that typically taper off on elements that are parallel to the rims.

Similar to Class 2, doubling goes toward the edge on Class 6 examples. Specimens are often found with some degree of Class 2 doubling present. Such examples may be hemispherical, in that, half the coin is largely reminiscent of class 6, and the other half is closer to Class 2. It is also common to have separation lines on Class 6 examples which suggests the expansion took place during more than one hubbing reinforcing the idea that there is a die steel compositional issue as the root cause for Class 6 (and possible some or all Class 2s).

Classic examples of class 6 include 1943 1c DDO-001; 1937 5c DDO-001; 1964 25c DDR-002.


Class 7 (VII) Modified Hub Doubling:
The suspected misalignment event for Class VII was rooted in the idea that there were remnants of a 7 underneath some 1958 Lincoln cents. The inkling was that a 1957 working hub was “modified,” when the 7 was ground off and an 8 engraved over it to make a new 1958 master hub. This has been disproven. Some 1970S Lincoln cents were, for years, classified as Class VII and have been revaluated to be from other hub doubling classes.

As of now only some 1941 Lincoln cents are designated as Class VII where part of the crossbar on the second T in TRUST broke. These isolated doubled die listings show hubbings from a normal hub and the broken T hub, or multiple hubbings with the broken T hub. The best example from this group is 1941 1c DDO-013.

Class 8 (VIII) Tilted Hub Doubling:
The premise of for the Class VIII misalignment event is that the hub was tilted on the die. Most examples show only a partial hubbing. If the die tilts from any given point outside the mid-section, a corresponding lateral movement of the hub, misaligns the perimeter of the hub with the die below. This will cause the doubling to go Inwards toward the center of the die. Along with the tilt the hub and inherent misalignment, there can be some rotation, a pivot or end up offset in any given direction. These additional hub movements are considered indirect and not noted as an additional level of misalignment unless they are equally paramount as the tilt. A hybrid example is 1939 1c DDO-001 that shows a rotation that is strangely hemispherical suggesting the die was also tilt making it a Class 1 + 8.

A good example of a definitive Class 8 is 1960 1c DDO-006 which shows partial doubling of IN, G from GOD, and the first T in TRUST. The northwest spread stemming from the hub being tilted and offset laterally southeast, would be enough to show the doubled areas without needing any additional types of misalignments.

Class 9 (IX) Single Squeeze:
When the working hub in a single squeeze hubbing press is set on a die blank untethered above, it can be at an initial tilt showing some horizontal deviation. Depending on the design used, the hub may sit on a precise spot at first contact. As pressure is exerted, the back of the hub will rock or jolt into its proper position creating doubling on the die face.

While Class 9 is tilted, it does not match the timing or sequence of class 8 tilted hub doubling. Class 8 typically resides along the periphery only, and needs a minimum of two hubbings, whereas Class 9 manifests during a single hubbing and can be located centrally or almost throughout the design.

There are two types of doubling:
Jolted (Type 1): mimics offset doubling, and is focused in a hot zone of the central design elements. Parts of a device are replicated in the adjacent open fields. They can be marginal, offset, or even show rotation. There is a maximum spread, and a limit to how much is duplicated. Typically, there is one region on a coin’s design where almost all doubling occurs. This can be surmised by similar doubling found on coins from Denver and Philadelphia. (e.g., 2009 Lincoln cents)

This type of doubling is created earlier in the hubbing, when the die can still jolt back into correct position leaving only a trace of doubling. It should be noted that doubling could be caused, at least on occasion, by the press being reset during a hubbing – there is no clear indication as to how often that occurs.

Decisive examples include: 2015P 25c NE DDR-004; 2009 1c FY DDR-002; and 2009D 25c DC DDR-001

Roly-poly (Type 2): The second type is characterized by an offset distorted extra thickness that is roly-poly in appearance. Doubling can manifest over a larger section of the die, including the periphery. Doubling is typically stronger centrally and weakens toward the edge of the design. The doubling is related to type 1, with horizontal play between the hub and die, but the point of contact seems unceasing, and instead of a jolt, it rolls under pressure extruding the design as the tilt stabilizes. On some examples, there is a wobble, accounting for notched corners and separation lines.

This type of doubling can be secluded to a small area or can be widespread. The doubling is unlike class 4 with milder separation lines, soft corner notching and a roly-poly extra thickness. It is unlike class 6, in that the distortion is offset, and does not distort toward the edge.

Key examples include: 2006 1c DDO-003; 2015 1c DDO-001; 2012P $1 BH DDO-001

Hybrid Doubling:
Above it has been noted several times that hybrid doubling happens. Within the CONECA files hybrid doubling is only noted when the two classes jointly create clarity to explain the observed doubling. Class 2 + 5 and Class 2 + 6 are the two most common hybrid scenarios. Class 9 should not be paired with another class without definitive proof the press was reset resulting in uncharacteristic movement between hubbings.

It is also possible for an unrelated punching issue to occur on the same die face such as a listing that includes an RPM or RPD. These are unusual and must viewed separately. The doubling from the RPM will not mirror that of the DDO or DDR.

Note: additionally, any given doubled die could be paired with an obverse or reverse that also has a doubled die; another uncommon scenario. Even rarer is a DDO and DDR paired with an RPM. Care must be taken when diagnosing worthless doubling from that of one of these extremely uncommon scenarios. If the coin in hand shows doubling all over the coin, it is more likely to be die wear or machine doubling than a multi die variety coin.

Die Stages, Die State & Die Markers:
Die Stages are included in the CML for two reasons: 1) to aid in the proper identification of a listed variety, and 2) to document the Die State (or die progression of the die).

Die stages should be aligned with die state: VEDS, EDS, EMDS, MDS, LMDS, LDS and VLDS. The only other cases that should justify a “new” stage is something dramatic which will help for attribution purposes.

Die markers are unique traces of events that have befallen a die. They include, but are not limited to, die scratches, die gouging, die dents, die damage, die clashing, die cracks, die chips, die breaks and even a misaligned die or die rotation. Note: die markers do not make the coin examined a particular variety – markers are used in unison with noted variety characteristics. Many die markers that exist on a variety can be surprisingly similar to marks on a non-variety coin. Do not assume otherwise.

Every effort is taken to be objective about die state and markers within the CML. Markers could be inadvertently overlooked, die state misinterpreted or a listing being misidentified as a new variety when it was really a stage of something listed previously. Die state on any given denomination or era will not be the same on another era. The composition of planchets has changed as well as the Mint ever improving the die steel used to make more coins per die.

Current INDEX of TERMS:
BIE = Die break between the letters of LIBERTY
CUD = Major die break notated when it relates to a die marker
DDO = Doubled Die Obverse
DDR = Doubled Die Reverse
IMM = Inverted MintMark
MDO = Master die Doubled Obverse
MDR = Master die Doubled Reverse
MMP = MintMark Placement
MMS = MintMark Style
MPD = MisPlaced Date
ODV = Obverse Design Variety
OMM = Over MintMark
RDV = Reverse Design Variety
RED = Re-Engraved Design
ROT = ROTated dies
RPD = RePunched Date
RPM = RePunched Mintmark
SDO = Series hub Doubled Obverse
SDR = Series hub Doubled Reverse
WHO = Working Hub doubled Obverse
WHR = Working Hub doubled Reverse

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