2012 01 16

High-bouncing
die leaves offset, incuse machine doubling

By
Mike Diamond-Special to Coin World | Jan. 07, 2012
9:56 a.m.

Article
first published in 2012-01-16, Expert Advice section of Coin World

This 2011-D Olympic
National Park quarter dollar shows incuse machine doubling affecting the
southeast arc of peripheral lettering (E PLUR). The bottom of each affected
letter is smeared, and a second set of letters peeks out above the normal
letters.

Images by Mike Diamond

In 2010, the U.S. Mint
began striking quarter dollars for its America the Beautiful program. Each coin
features a reverse design that celebrates a national park or other site of
national significance. A raised perimeter ring on the reverse face houses an array
of incuse design elements.

The presence of these
incuse elements raises the odds of seeing new or unusual effects, even in so
humble an error category as machine doubling.

Machine doubling
occurs immediately after the hammer die has reached the lowest point of its
downstroke. It generally reflects instability in the die, die assembly or the
coinage press as a whole.

In some cases, either
die can rebound from the surface of the coin, shift laterally and land lightly
on the newly struck design elements. This produces marginal shelving at the
edge of the design, but can result in clear duplication of interior design
details.

In other cases, a die
simply shifts laterally after the hammer die reaches its lowest point. This
causes smearing of the newly-struck design and the piling up of relocated metal
into a series of ridges.

Raised and incused
designs

While the same die
motions affect both raised and incuse design elements, the resulting appearance
is rather different in the latter. This has caused some cases of incuse machine
doubling to be mistaken for a doubled die (hub doubling), a mishap that results
from multiple impressions of a working hub into a working die. An example of
deceptive machine doubling in a 2010 Grand Canyon National park 5-ounce silver bullion
coin was recently discussed by Ken Potter (http://numismaster.com/ta/numis/Article.jsp?ad=article&ArticleId=17345).

A commemorative
quarter dollar recently found in pocket change by Alex Tuel further illustrates
the ease with which incuse machine doubling can be mistaken for other sorts of
minting errors and die varieties. The coin in question is a 2011-D Olympic
National Park quarter dollar.

Tuel first presented
his specimen on the message board of Lincoln Cent Resource (www.lincolncentresource.net/forums/showthread.php?t=17470&page=3).
Photographs provided by Tuel showed a second set of overlapping letters (E
PLUR) that were offset and independent from their normal counterparts. The
extra letters are much thinner than the normal ones.

Early opinions
gravitated toward a doubled die or a Type II counterclash. The latter is a form
of patterned die damage that results when a hard piece of metal is struck twice
(see Collectors’ Clearinghouse, Sept. 29, 2008).

I suspected machine
doubling (as did others), but couldn’t be sure just by looking at the photos.
So I asked Alex to send me the coin and he generously obliged. An examination
under a microscope confirmed my suspicions.

The bottom (outer)
portions of the letters E PLURIBUS show conspicuous smearing, a sign of
unwanted movement in the reverse (hammer) die or hammer die assembly. The
second set of letters was evidently caused by a high bounce of the hammer die
after it reached the lowest point of its downstroke.

Forming incused
letters

Remember that the
incuse letters on the coin are created by raised letters on the die face that
extend well beyond the plane of the surrounding field. In this series, the
perimeter ring is recessed on the die face and the letters stick up from its
floor. The hammer die’s bounce would have carried those raised letters
completely out of the recessed letters they’d just created. A slight shift to
the northwest positioned those raised letters directly above the raised
perimeter ring of the coin. Descending from the apex of its bounce, the hammer
die made light contact with the coin’s perimeter ring. This light impact
produced the second set of letters in the field. The reason they’re so thin is
that, in cross-section, the apex of each raised letter is narrower than its
base, and only the apex left an impression.

A high bounce with a
strong lateral shift will sometimes generate odd effects on coins with
conventional raised designs. Previous installments of Collectors’ Clearinghouse
introduced the phenomenon of “rim-restricted design duplication” (Feb. 22,
2010, Aug. 22, 2011). This form of machine doubling leaves an entirely separate
set of raised design elements on the newly-formed design rim.

Coin
World’s Collectors’ Clearinghouse department
does not accept coins or other items for examination without prior permission
from News Editor William T. Gibbs. Materials sent to Clearinghouse without
prior permission will be returned unexamined. Please address all Clearinghouse
inquiries tocweditor@coinworld.com or to 800-673-8311,
Ext. 172.

http://www.coinworld.com/articles/high-bouncing-die-leaves-offset-incuse-machin/