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
