Search Results for: Ridge ring

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.

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/

Copyright
2012 by Amos Hobby Publishing Inc. Reposted by permission from the March 22,
2012, issue of Coin World.)

A second case of abnormal reeding on a State quarter dollar

By Mike Diamond-Special
to Coin World |
April 07, 2012 9:58 a.m.

Article first published in 2012-04-16, Expert Advice section of Coin World

A side-by-side comparison of two 2008-P New
Mexico quarter dollars, one with normal reeding, bottom, and one with abnormal
reeding, top. The apex of each ridge on the working face of the collar was
truncated by abrasion.

Images by Mike Diamond.

A wise old aphorism from the realm of science declares that “fortune favors the prepared mind.”

Marilyn Keeney’s mind was certainly prepared when she stumbled across a second example of abnormal reeding in a State quarter dollar.

The first example — also discovered by Keeney — was reported in the Jan. 25, 2010, Collectors’ Clearinghouse. Back then she encountered a group of 2008-P New Mexico quarter dollars struck within a single damaged collar. As shown in the accompanying photo, the reeds (vertical ridges) on the edge of each affected coin are unusually low and narrow and are separated from each other by abnormally wide, flat valleys. This appearance reflects damage to the sharp tips of the corresponding ridges on the working face of the collar. The apex of each ridge was removed by abrasion or machining. Horizontal scratches in the valley floors seem to point to the use of some kind of rotating, cylindrical device.

The original discussion also included a much earlier case involving a 1964-D Washington quarter dollar. That example showed a similar, but somewhat less uniform pattern of low, narrow reeds and broad, flat valleys.

The same sort of collar damage has now been found on the edge of some 2007-P Wyoming quarter dollars. Here the damage is not nearly as severe as that seen in the earlier examples. The damage also affects only about half the edge. The edge exhibits a gradual transition from normal reeding to abnormal reeding, with the widest valleys seen at around 8:00 (obverse clock position).

At least three die pairs are represented within a group of five quarter dollars that were found by Keeney. This is not particularly surprising, as the same collar is often used through several die changes. Keeney’s two finds leave little doubt that many other cases of similar damage are yet to be discovered. In fact, I stumbled across another example while rummaging through my modest collection of coins with odd-looking reeding. This time the collar damage was detected on a 1967 quarter dollar that combines a tilted partial collar with an uncentered broadstrike. In other words, the collar was strongly tilted and a portion of it was positioned beneath the plane of the anvil (reverse) die face. The reeds are low, narrow and widely spaced (see photos).

A particularly interesting feature is seen at 2:30. Here the reeds taper strongly as they approach the top of the collar. The same phenomenon is seen on the 1964-D Washington quarter dollar. This provides a clue as to the likely cause of the damage in all these examples.

In many collars the entrance is beveled. Judging from a large sample of partial collar errors, the length of this beveled transition zone between the top of the collar and its working face is highly variable. A sloping entrance deflects the impact of a misaligned hammer die, helping to prevent damage to both the die and the working face of the collar. It also probably makes for more reliable insertion of the planchet.

In either case, the damage would be expected to occur most frequently, and achieve its greatest severity, along the upper portion of the collar’s working face. This neatly explains why the reeds sometimes taper toward the obverse face and the top of the collar.

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/a-second-case-of-abnormal-reeding-on-a-state-/

Copyright
2012 by Amos Hobby Publishing Inc. Reposted by permission from the March 22,
2012, issue of Coin World.)