A concise description of how doubled dies occur
by J. T. Stanton, N.L.G.
When the term doubled die is used, we are commonly referring to
a coin which has a doubled or partially doubled image, letters, and/or
numbers. However, a doubled die is actually a die which exhibits
this doubling, and any coin struck from this die will exhibit this
doubling. The correct terminology for the resulting products of doubled
dies would be doubled die coins.
How Doubled Dies Occur – The Hubbing Process
So that we may understand how the doubling occurs on the dies themselves, we must first take a look at the hubbing process; the production of the dies.
Once the coin design has been approved, it is then modeled on plaster in relief (positive), just as it will appear on the coin. The next step is to coat the plaster with epoxy resins to create a surface hard enough to withstand the next process. This epoxy coated model is called a galvano. The galvano is usually 12 to 15 inches in diameter.
The next step is to reduce the design on the galvano to the actual size
of the coin to be produced. To accomplish this, the Mint uses a Janvier
Transfer Reducing Machine. This machine, operating on the principle of
a fulcrum, will trace the design on the galvano. This is accomplished by a
long metal arm with a tracing stylus on one end as the galvano rotates.
The tracing will be transferred to the opposite end, where a sharp cutting
tool is positioned. This cutting tool will be carving the design exactly
as it is traced from the galvano onto the end of a steel bar. This steel
bar will usually be about 2 inches in diameter, and tapered so that the
end being cut will be the actual size of the coin to be produced. The
steel bar will also be rotating, however at a slower speed, so that the
design being traced from the galvano will be properly transferred. The
process will usually be duplicated at least once to ensure proper
sharpness of the design. Once complete, the steel bar will become what is
known as the master hub (sometimes called “hob”), with
the design again in relief, as it will appear on the finished coin.
The master hub is then placed into a hydraulic press, known as a hubbing
press, opposite another blank steel bar. These steel bars, usually
about 6 inches long, are hardened steel. Several hundred tons of force
will be applied as the master hub and the raw steel bar are brought
together. This process will “squeeze” the design on the master
hub into the steel bar. After one impression, the new steel bar will be
taken to an annealing furnace, where it will be heated to extreme
temperatures to soften the steel for the next impression. When cool, the
new steel bar will again be impressed with the master hub. This process,
known as hubbing, must be performed at least twice to bring the
design up to the desired sharpness. Once the desired sharpness of detail
is achieved, a master die will have been created, with the design
incused (mirror image). Depending upon the design and denomination, the
hubbing process may need to be repeated as many as 15 times. This is the
first point at which doubled die can occur.
There is generally one master hub produced, and possibly two master dies. The master die will create a working hub, again in the same manner asdescribed above (hubbing), and with the design in relief as it will appearon the coin. Working hubs are used to create working dies, with thedesign incused (mirror image). Generally, several working hubs will beproduced, and hundreds of working dies. Doubled dies can occur during any of the above mentioned hubbing operations if the die and hub are not nproperly aligned.
The sequence then is as follows:
1. Design approved
2. Plaster model
3. Plaster model epoxy coated (galvano)
4. Reducing machine to produce master hub
5. * Master hub produces master dies
6. * Master dies produce working hubs
7. * Working hubs produce working dies
8. Working dies produce coins
* Doubled dies can occur at these stages
The Classes of Doubled Dies
There are currently eight different types or classes of doubled
dies listed. These different classes are described and named based upon
the method in which the particular doubled die occurred.
It is important to use the correct terminology. “Double die”
would represent two dies, and as you know, we are dealing with a single
die, with a final product which has a doubled (past tense) image,
so therefore, doubled die is the correct term.
It is also important to note that in the descriptions that follow, we
often refer to the hub entering the die when explaining how the various
classes of doubled dies occur. We chose this explanation for simplicity,
but keep in mind that doubled die doubling can occur when the master hub
is impressing the master die, when the master die is impressing the
working hub, and when the working hub is impressing the working die, or a
combination of any of these. We are referring to doubled dies in
this text, but you should keep in mind that we are also taking about any
die with a multiple image. Tripled and quadrupled dies are known to exist,
and they are in this same family of die varieties.
One final note; keep in mind that the different classes of doubled dies
are numbered and identified with Roman numerals, and not Arabic
|Rotated Hub Doubling
Distorted Hub Doubling
Design Hub Doubling
Offset Hub Doubling
|Pivoted Hub Doubling
Distended Hub Doubling
Modified Hub Doubling
Tilted Hub Doubling
Class I Doubled Dies – Rotated Hub Doubling
This class occurs when the hub, after the initial impression into the
die, is rotated slightly either clockwise or counter-clockwise around an
axis in the center of the coin design prior to being re-entered into the
die. The images around the rim will be of equal spread, and the spread atthe rim will be greater than that nearer the center of the coin. The mostwell known class I doubled die is the 1955 Lincoln Cent doubled dieobverse.
Class II Doubled Dies – Distorted Hub Doubling
This class occurs when a die is used for one hubbing, and a die with a
distorted hub used for a subsequent hubbing, creating an image
overlapping, and spread irregularly toward the rim. The process could also
create a die which was hubbed initially with a distorted hub, then
subsequently with a fresh hub, creating a spread in the opposite
directing. The spread will be defined either toward the rim or toward the
center of the coin.
Class III Doubled Dies – Design Hub Doubling
This class is caused when a die is hubbed with a hub of one design, and
a second hubbing with a hub with a different design, or the same design
but with slightly different positioning. The 1943/2-P Jefferson nickel is
a good example.
Class IV Doubled Dies – Offset Hub Doubling
This form of doubling is caused when one impression of the hub into the
die is offset in one direction from the other. A well known example is the
1983 Lincoln cent doubled die reverse.
Class V Doubled Dies – Pivoted Hub Doubling
This form of doubling is caused when the die after its initial
impression is mis-aligned with the hub a second time in a fan shape
direction. The pivot point will usually be near the rim, and the doubling
will be strongest opposite the pivot point. A good example of this
doubling is the 1917 Lincoln cent doubled die obverse.
Class VI Doubled Dies – Distended Hub Doubling
This form of doubled die is the most difficult for many novices to
identify, as it will rarely exhibit any separation of the two images. A
die may be hubbed with greater than normal pressure, then hubbed again
with normal pressure, but with the design in a slightly different
position. This will create a single image, but with thicker than normal
letters and numbers, with little or no trace of doubling.
Class VII Doubled Dies – Modified Hub Doubling
A hub that was modified or changed so that all or part of the design
element was left on the hub in or around the same or a different design
element, so that all or part of both design elements were transferred to
every die made with that hub, and all or part of both appear on the struck
Class VIII Doubled Dies – Tilted Hub Doubling
A die that was hubbed normally the first time, but the hub or die was
tilted for a subsequent impression so that the hub either made partial
contact with the die at one point, or a full impression that was deeper at
one edge than at the other. This will show on the struck coin as a
displaced part of the design or a tapering amount of relief across the
face of the coin.
The descriptions above describe the various classes of doubled dies.
However, it is possible to have a doubled die coin exhibit two or more
different classes. A good example is the 1971-S proof Lincoln cent listed
as 2-O-II+V. This variety exhibits both the class II and class V doubling,
as the secondary image is slightly toward the center of the coin, and also
pivoted. The pivoting explains why the doubling is evident on LIBERTY, but
not on the date.
Descriptions taken in part from Alan Herbert’s book Official Price
Guide to Minting Varieties and Errors. Alan is the catalyst behind
most of out current knowledge of Mint errors and varieties.
Copyright 2000 by J. T. Stanton.
This article may be reproduced in its entirety, as long as the source is
J. T. Stanton
P. O. Box 15487
Savannah, GA 31416-2187