Defects in working hubs tend to be small and easy to overlook. They
also don’t occur very often.
A working hub is a steel cylinder that carries a coin’s design in
bas relief. In other words, the design is identical in size and
appearance to what you would see on a coin.
The working hub is used to fabricate a number of working dies. The
process involves the working hub being slowly squeezed into a second
cylinder (the blank working die) under enormous pressure. The working
die is softer than the working hub because it is annealed
(heat-treated) prior to hubbing. This “relaxes” the crystalline
structure of the metal, making it more malleable. Depending on the
mint and the time period involved, one or more squeezes are necessary
to fully transfer the working hub’s design to the working die.
Just like a working die, a working hub can experience brittle
failure. Examples of brittle failure in working hubs tend to be quite
modest and fall into the category of “hub chips,” affecting the
Among U.S. coins, a well-known example of a chipped working hub
can be found among 1936 Lincoln cents. In this case the left leg of
the R of LIBERTY has broken off.
I recently purchased an entire roll of these cents (all
well-circulated) from Chris and Charity Welch. It was difficult to
discern microscopic die markers on the heavily worn surfaces of these
coins. Nevertheless, among these 50 examples, I could identify a
minimum of three die pairs, indicating that the hub chip escaped
notice for quite some time as it was used to hub a succession of dies.
The sheer abundance of these cents would independently support the
presence of multiple die pairs.
Other chipped hubs are even more insignificant. Several are
depicted on the Lincoln Cent Resource website (www.lincoln
thread.php?t=30866) with links to
other images. Not mentioned there is a 2002 Lincoln cent I recall
seeing in which the left corner of the first 2 was chipped off.
Larger hub chips can be found among world coins. The reverse face
of a 1972 Colombia 10-centavo coin shows a hub chip affecting the
numerical portion of the denomination. The left side of the 1 in 10
has chipped off.
This example displays a feature useful for distinguishing between
chipped hubs and unrelated errors that look superficially similar.
You’ll notice that the missing portion of the 10 is still visible in
the form of a sunken trace. When a piece breaks off a design element
on the hub face, it sometimes carries away metal lying slightly below
the plane of the hub’s field.
Not shown is the obverse face of this 10-centavo coin. It displays
a strong doubled die.
Another 1972 Colombia 10-centavo coin shows two hub chips on the
obverse face. For both Os of COLOMBIA, the bottom portion is missing.
This chipped hub co-occurs with a strong tripled die on the same face.
The tripling demonstrates that the working hub was squeezed at least
three times into the working die, with offset between hub and die
occurring in each instance.
Chipped hubs are easily mistaken for filled die errors. The latter
error occurs when die fill (“grease”) — a mixture variably composed of
lubricant, metal dust, and dirt — completely fills a recess in the die
face without spilling over onto the field. A chipped hub can be
distinguished by the following diagnostics:
(1) The missing portion of the design element is sharply and
abruptly demarcated. Filled die errors often show a softer margin.
(2) As mentioned above, a chipped hub may show a sunken outline of
the missing portion of the design element.
(3) If the identical defect is found on many examples, and
especially if more than one die is involved, there can be no doubt
that a chipped hub is responsible.
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coins or other items for examination without prior permission
News Editor William T. Gibbs. Materials sent to
Clearinghouse without prior permission will be returned unexamined.
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