Among the myriad striking errors known to hobbyists, the edge
strike ranks among the rarest. An edge strike is exactly what the name
implies — a coin struck on-edge.
An undated Lincoln copper-plated zinc cent illustrated this week
provides a typical example. Die-struck design elements can be found at
opposing, flattened poles. The planchet itself is strongly bowed.
This planchet may have entered the striking chamber spinning on
its edge. Perhaps it rolled into a striking chamber on its edge. Or it
could instead have been kicked into a vertical position when another
planchet or coin was knocked into it. Maybe it flew into the striking
chamber, flipping end-over-end, and was caught by the descending
hammer die at just the right moment. All we can be sure of is that the
planchet was not perfectly vertical when it was struck. If it was, it
would have been converted into a foldover strike. Owing to its slight
tilt, the planchet was propelled from the striking chamber as the
hammer die compressed it.
Given the rarity of simple edge strikes, we would expect double-
and triple-struck examples to be nearly unobtainable. Surprisingly,
they seem just as abundant as the conventional type. Factoring out
secure examples such as normal coins that are secondarily struck
on-edge, we still have an uncomfortably large number of claimants. I
think part of the answer is that many of these purported multi-struck
edge strikes are the product of a single downstroke (a double strike,
by definition, requires two downstrokes).
These dubious double strikes fall into two categories. The first
category is illustrated this week by a 1996 Lincoln cent. It features
an edge strike at the pole struck by the obverse die and an off-center
strike that encompasses the opposite pole. Such coins are often
interpreted as conventional edge strikes that receive a second
off-center strike that overlaps (and erases) one of the edge-struck
poles. The characteristic antipodal positioning of the two strikes
suggests a simpler explanation. It’s more likely that the planchet
received an edge strike in the early phase of the downstroke, slipped,
fell on its side and was struck again as the hammer die completed its downstroke.
The second category of dubious double strike is represented here
by a 1998 Lincoln cent. It features an edge strike at the
obverse-struck pole, a highly asymmetrical (“paraxial”) foldover
strike at the reverse-struck pole, and a slightly off-center strike
between them. The foldover flap is embedded in the reverse face. I’ve
seen more than a half-dozen similar examples.
Coins like the 1998 cent are usually described and encapsulated as
double strikes and one time as a triple strike (see Collectors’
Clearinghouse, Dec. 28, 2009). Once again, however, their highly
consistent appearance suggests that a single downstroke was responsible.
The simplest explanation involves the following sequence of
events. The planchet is first struck on-edge during the initial phase
of the hammer die’s downstroke. As the hammer die continues its
descent, the planchet begins to bend in the middle (an “axial bend”).
As the pressure rises the planchet slips and falls on its side, with
the axial bend facing upward toward the hammer die. While all this is
happening, a second bend is developing at the pole in contact with the
anvil die. This pole — temporarily caught in the recesses of the anvil
die — develops a paraxial fold. It’s not clear whether the metal
adjacent to the point of contact is stretched out or distinctly
folded. For the larger flaps, it’s probably the latter. Regardless of
the mechanism, it’s enough to create a small, semicircular flap that
is tucked beneath the bent planchet.
The final step entails the hammer die completing its descent,
creating the central strike. This flattens the axial bend and embeds
the small flap into the reverse face. Stress cracks running at a right
angle to the axis connecting the edge strike and the foldover flap can
usually be seen in the copper plating. This marks the location of the
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