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2011 05 30




Machine
parts above collar can impede expanding coins


By Mike Diamond | May 21, 2011
10:00 a.m. 

Article
first published in 2011-05-30, Expert Advice section of Coin World



An
off-center cent with a “sideneck strike.” Driven toward the northeast by the
expanding die-struck portion of the coin, the unstruck edge collided with the
side of the adjacent hammer die neck.


Images by Mike Diamond.

As
a coin is struck, its expansion is abruptly halted by the surrounding collar.


When
the collar fails to deploy, a coin expands in all directions. As a result, all
off-center strikes and broadstrikes are wider than a normal coin, to varying
degrees.


On
some occasions a coin’s expansion is impeded, and the edge damaged, by machine
parts positioned above the collar plate.


The
most familiar obstacle to unfettered expansion is the neck of an adjacent
hammer die. In a dual or quad Bliss press (the last of which was retired in
2005), the close proximity of adjacent die pairs results in the occasional
production of a “sideneck strike,” also referred to as an “almost saddle
strike” or a “one-die saddle strike.”


A
typical example is shown here in an off-center Lincoln cent. At the pole
opposite the 1 o’clock position of the obverse face, we see a deep, concave
notch and an associated pressure ridge. The planchet represented by this coin
lay partly within one striking chamber and almost managed to encroach on the
adjacent striking chamber. In other words, the coin fell just short of becoming
a “saddle strike.” When struck, the expanding die-struck area pushed the
unstruck portion toward the adjacent striking chamber. It collided with the
side of the hammer (obverse) die neck as the latter was striking its own coin.


Sideneck
strikes are always concave and always closest to the adjacent striking chamber.
In most years, this chamber would lie along a line drawn from the 1 o’clock
position in Lincoln cents, or the 11 o’clock position in Jefferson 5-cent coins
and Roosevelt dimes.


Strike-related
edge damage of another kind is seen in an undated Jefferson 5-cent coin. The
pole opposite the off-center strike has a flat, vertically oriented contact
facet. It appears that the facet was produced when the unstruck portion of the
planchet was pushed south by the expanding die-struck area and collided with a
machine part. Another possibility is that the coin was hit while momentarily
immobilized by the two dies.


In
either case, we can’t be sure what machine part was responsible, although I
suspect a feeder finger. I’ve encountered these flat facets on quite a few
off-center and double-struck cents and 5-cent coins. In each case, the strike
is about 70 percent off-center and the contact facet lies opposite the base of
the bust.


The
introduction of the Schuler press introduced new types of strike-related edge
damage. This press uses a single die pair, with the reverse die operating as
the hammer die. The damage is primarily associated with multi-struck coins. A
representative example is provided by a quadruple-struck 5-cent coin. The first
strike was normal. The other strikes were delivered about 20 percent off-center
and are closely spaced. Edge damage is present on both the right and left
sides. The contact facet on the right side is convex, slightly beveled, and
extends from 12 o’clock to 2:30.


The
dies evidently struck whatever machine part rested against the coin. On the
left side the coin buckled when it collided with a hard object. The contact
facet here is quite compact and lies next to the w of we. It’s possible that
the coin was pushed laterally into an obstruction by expansion produced by the
off-center strikes. It’s also possible that an object hit the coin as the
latter was temporarily immobilized between the dies.


This
type of edge damage can be found on numerous multi-struck cents, 5-cent coins,
and Washington quarter dollars struck by Schuler presses. The pattern is
consistent, although the long facet and the short facet can be located on
either the right or the left side.


The
affected coins all show a sequence of strikes involving a normal (or at least
centered) first strike, and one or more closely spaced off-center strikes.
Coins in which the off-center strikes are widely spaced or erratically
positioned typically do not show this edge damage. The long facet that hugs the
edge of the off-center strikes is almost certainly caused by contact with a
feeder finger. I’m not sure about the short facet.


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/machine-parts-above-collar-can-impede-expandi/



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


2011 12 26




2011-12-26



Concentric
‘strike lines’ don’t always indicate multiple strikes


By Mike Diamond-Special
to Coin World |
Dec. 17, 2011 9:59 a.m. 

Article
first published in 2011-12-26, Expert Advice section of Coin World


 


Four concentric strike lines formed on
the reverse face of this broadstruck 2000-P Jefferson 5-cent coin. The faint
concentric lines in the field are unrelated. They are concentric lathe marks —
a die error.


Images by Mike Diamond.



Multiple
strikes are often hard to spot when no movement of the coin occurs between
strikes. Collectors rely on a number of diagnostic clues to identify such
“close multi-strikes.” One such clue is the presence of concentric strike
lines.


Concentric
strike lines are circular or semicircular grooves or steps produced by the edge
of the field portion of the die and sometimes the outer edge of the rim gutter
of the die. An intermediate strike line can reflect the presence of collar
clash, which occurs when the rim gutter is damaged by contact with the top of
the collar. Close examination of spacing, contour and stepwise elevation of the
strike lines is necessary to distinguish those created by multiple strikes from
those that simply result from contact with different parts of the die
perimeter.


Strike
lines are located in the “slide zone” of off-center and broadstruck coins. The
slide zone forms as coin metal squeezes out between the dies and picks up fine
radial striations in the process. A strike line interrupts these striations.


It
would be nice if strike lines always indicated the presence of extra strikes,
but this is not the case. For example, they sometimes form opposite a “stiff
collar” error. The planchet represented by the illustrated 2000-P Jefferson
5-cent coin was not perfectly centered in the striking chamber when it was
struck. The right side rested against a stiff, but still mobile collar. The
obverse face (struck by the anvil die) was left with a sloping, featureless
shoulder that terminates laterally in a strong collar scar. On the reverse
face, four concentric strike lines can be detected between the edge of the
field and the unstruck portion of the planchet.


The
multiple strike lines were produced early in the downstroke as the hammer
(reverse) die skittered across the surface of the planchet as the collar
collapsed.


These
strike lines happen to be a minor expression of a Type I stutter strike. Had
the bounces been higher and wider, a thin crescent of die-struck design would
have been left in the gap between the inner and outer series of strike lines. A
Type I stutter strike is shown in the Dec. 28, 2009, “Collectors’
Clearinghouse” column.


I’m
not sure what caused the extensive series of strike lines present on the
obverse face of the illustrated 1993-P Washington quarter dollar. The broad
crescent on the left carries no fewer than six concentric lines. I doubt they
represent an incipient stutter strike.


On
the reverse face, strangely distant from the die-struck design, are two short but
very deep arcs of collar contact, located at 6:00 and 8:30. At this distance,
I’m skeptical that the collar could have provided sufficient resistance for
even a loose hammer die to skitter. This hypothesis would also have to
incorporate the unlikely assumption that the hammer (obverse) die contacted the
planchet in a very misaligned position and that it skittered its way to a
centered position by the time the downstroke was completed.


An
equally dubious scenario has the planchet squeezing out beneath a jittery
hammer die. Instead of a “slide zone” forming with conventional radial
striations, a series of partial rings was generated. The stumbling block here
is that this presumptive slide zone is far too wide relative to the strength of
the strike, which was quite modest. The slide zone on the reverse face is
extremely narrow.


Almost
as puzzling are the two to three concentric strike lines present on the left
side of the reverse face of a broadstruck 1998-D Roosevelt dime. The coin shows
are no signs of collar contact at all, which would seem to rule out a Type I
stutter strike. Here, at least, it seems possible that the planchet squeezed
out beneath a jittery hammer (reverse) die, leaving a series of curved lines.


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 


http://www.coinworld.com/articles/concentric-strike-lines-dont-always-indicate-/



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


2012 03 19

‘Two-tailed’ Canadian cents: mules or pseudo-mules?

By Mike Diamond-Special to Coin World |
March 10, 2012 9:58 a.m.

Article first published in 2012-03-19, Expert Advice section of Coin World

This multi-struck, double-reverse Canadian cent takes the form of a die cap. It could be a two-tailed mule (struck by two reverse dies) or a pseudo-mule.

Images by Mike Diamond.

 

 

On page 197 of World’s Greatest Mint Errors (Zyrus Press, 2009), author Mike Byers features a multi-struck 1978 Canadian cent with the reverse design on both faces. The extra strike(s) transformed the coin into a die cap with impressively high walls (see photos).

These details are beyond dispute. What can be questioned is the coin’s status as a two-tailed mule. A mule is a coin struck by mismatched dies. Both Byers and Professional Coin Grading Service state that the coin was struck by two reverse dies, one acting as hammer die and one as the anvil die.

It’s important to note that ordinary Canadian cents are invariably struck with the reverse die acting as the hammer die (the hammer die delivers the impact while the anvil die receives the impact).

Possible pseudo mule?

There’s another, equally plausible diagnosis — that this is a two-tailed pseudo-mule (false mule). Despite carrying the same design on each face, a pseudo-mule is struck using a conventional die setup. The 1978 Canadian cent’s current owner, Chef Ito, sent it to me after I mentioned this possibility.

se events can occur spontaneously or with human assistance. Regardless of its etiology, I strongly suspect that Ito’s coin had help. In 1978 a flood of highly improbable errors emerged from the Royal Canadian Mint, many bearing the cent design.

Dia

A pseudo-mule incorporating the maple leaf design on each face can be created in several ways.

(1) A cent is struck normally, flips over, and lands on top of another planchet. A second strike flattens the original Maple Leaf design while the queen’s bust is obliterated. The double thickness, and the associated increase in effective striking pressure, facilitates complete erasure of the bust.

(2) Two planchets are struck together within the collar, creating two in-collar uniface strikes. In other words, each coin has a blank face. The bottom coin is ejected, while the top coin flips over and lands on another planchet. The original Maple Leaf design is flattened, while the original featureless surface is struck by the hammer die.

(3) A cent sporting an in-collar first-strike brockage of the Maple Leaf design on its bottom face flips over (a brockage is an incuse, mirror-image version of the design). Another planchet is fed on top of the brockaged coin and is struck into it. The bottom face of that newly-struck coin carries a first-strike counterbrockage of the Maple Leaf design.

The

gnosis uncertain

Despite careful study, I was unable to determine if Ito’s coin is a mule or a pseudo-mule. Based on appearance alone, both scenarios seem equally plausible. But from the standpoint of process, a pseudo-mule would seem more likely. Chris Pilliod explained why in an Oct. 2, 2000, Coin World article on a two-headed 1859 Indian Head cent. In most presses, the anvil die has a longer neck than the hammer die. This allows the anvil die to move up and down within the collar and bring the newly-struck coin into the path of the ejection finger. A hammer die installed in the anvil die’s position could not perform this function and, more importantly, could not bring a planchet within range of the properly installed hammer die for a strike.

For a hammer die to act as an anvil die, you need to machine a longer neck. That requires time, equipment, expertise and most problematically, a wider conspiracy. One press operator, working quickly, can create an intentional pseudo-mule. This is probably why all Malaysian double-obverse 1-sen coins show the diagnostic characteristics of a double-struck pseudo-mule (see Feb. 8, 2010 and April 25, 2011, issues of Coin World).

Other Canadian rarities

Two other double-reverse Canadian cents (1980) have been reported (Coin World, Oct. 1, 2001). Both were described and encapsulated as mules. However, both coins show features consistent with a pseudo-mule (see photos of one of the examples, to the left).

(1) One face (“side A”) is sharply struck while the other (“side B”) shows flatter relief and softer details. PCGS reported side B as being “rougher in appearance” while Superior Galleries described a “frosty” surface texture. Both organizations thought Side B was struck by a worn die. However, these attributes are wholly consistent with a second strike against a planchet. Such impacts not only flatten the design, but they often cause a coarsening of the metal crystallites, leaving a matte texture.

(2) Side A has a finned rim. Abnormally high striking pressure caused coin metal to squeeze into the gap between die neck and collar. Two stacked discs could easily have been responsible for an increase in effective striking pressure.

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 to cweditor@coinworld.com or to 800-673-8311, Ext. 172.

http://www.coinworld.com/articles/two-tailed-canadian-cents-mules-or-pseudo-mul/

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

MD-11

 

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.)

 

Straight Clips

Part V. Planchet Errors:

Blanking and Cutting Errors:

Straight clips

Definition: A straight clip is thought to result when a blanking die (punch) slices through the leading or trailing end of the coin metal strip.  This pre-supposes that the ends were trimmed prior to the coil being fed into the blanking press.

Another possibility is the blanking die slicing through one side of a strip that is too narrow.  This situation might arise if the splitter, which divides the original wide strip into narrower slips, is not positioned right in the middle of the coil.

A small percentage of straight clips mark the termination of a planchet taper.  This may be where the rollers squeezed the leading or trailing end of the strip down to an abnormally thin gauge.

The edge texture of a straight clip is highly variable.  It can be smooth, rough, irregular, or serrated in some fashion.  This probably reflects a variety of machines employed for the task — shears, saws, guillotines are three possibilities.

A straight clip appears on a coin as a straight edge.  Not all straight edges are straight clips, however.  They are sometimes confused with chain strikes, broken planchet and broken coin errors, and various forms of pre-strike damage.  When a straight-clipped planchet is struck out of collar, the straight edge often bows out due to the pressure of the strike and attendant expansion of the coin.  These secondarily convex straight clips have been mistaken for elliptical clips.

For expanded treatment concerning clip diagnostics click here.

 

Depicted below is a 10 nuevos pesos Mexican bi-metallic with an extremely rare straight clip of the outer ring. This coin has also been struck off-center. 

 

 

Below is a 2001-P Jefferson nickel with a combination curve and straight clip.
Image courtesy Ynes Zavala

 

 

The below sequence of images illustrate metal flow and the taper and fadeout of the design rim. This is what we would expect to see when dealing with authentic straight clips. Top images include both faces of a Jefferson nickel and Lincoln wheat ear cent.
Illustration courtesy of Jason Cuvelier

 

 

The illustration below shows the overlapping punches on the coin
metal strip and what hypothetically could happen if the punches (red
arrows) went over the leading or back edge of the metal strip; if the
strip was not cut straight; if the strip was
too narrow; or if the strip was somehow fed into the blanking press at
an angle. All would result in some configuration of a straight clip as
shown in green

Illustration courtesy of Jason Cuvelier

 

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