The rarest form of machine doubling is one-sided, rim-restricted
design duplication (often shortened to rim-restricted design
duplication or RRDD).
Previously illustrated examples show die-struck letters (or other
die-struck elements) decorating the design rim at one pole of the face
struck by the hammer die (Collectors’ Clearinghouse, Feb. 22 and May
24, 2010; Aug. 22, 2011). These extra elements were produced when the
hammer die bounced up from the newly struck coin, shifted to one side,
and landed lightly on the design rim. Previously described domestic
cases include several 1994 Lincoln cents from at least two die pairs
(obverse face), a 2004 cent (reverse face), a large number of
Washington dollars (reverse face), and scattered examples from other
Presidential dollars issues ending with James Madison (reverse face).
Rim-restricted design duplication is therefore associated both with
“traditional” die setups (obverse die as hammer die) and with
“inverted” die setups (reverse die as hammer die).
A longstanding assumption
My longstanding assumption that RRDD would necessarily involve the
hammer die made complete sense at the time. Lateral movements of
hammer die (and die assembly) are not constrained by any independent
physical barrier. By contrast, the anvil die is closely confined by
the surrounding collar. Any lateral movements of the anvil die would
have to be severely limited. I suspect this is the reason why all
forms of machine doubling associated with the anvil die tend to be
more modestly developed than with the hammer die.
I was therefore quite surprised by a 1987-D Lincoln cent found by
George Antenucci that shows faint die-struck letter traces along the
northern arc of the reverse design rim. I am certain that the reverse
face of this coin was struck by the anvil die. T
he earliest experiments in striking modern issues with inverted
dies didn’t begin until 1992. This arrangement didn’t become common
until 1998 and only became the dominant setup in 2002.
Traces of STATES OF AMERICA are found along the inner margin of
the design rim. Despite the fact that they’re die-struck, most of the
traces are incuse. The incuse traces are not impressions of the letter
recesses in the die face. Instead, they are impressions of thin ridges
in the die face that capped each letter recess. The ridges are a
manifestation of die deterioration that left corresponding valleys in
the coin. Incuse forms of die deterioration can be found in many
denominations. Only the very top of the second S of STATES is actually
represented by a raised trace on the design rim.
The extent of lateral movement implied by these feeble imprints
are difficult to reconcile with the anvil die’s close confinement by
the collar. Something more complex must have transpired.
Increased lateral play could be the result of an abnormally wide
collar. However, the diameter of this coin is normal (19.05 millimeters).
Another possibility, though unlikely
Another possibility is “ejection doubling.” It has been claimed
(but never proven) that a coin will occasionally resist being pushed
off the face of the anvil die by the ejection mechanism. This would
cause a smearing of design elements (an effect that happens to be
indistinguishable from slide doubling caused by die instability).
However, none of the normal letters or letter traces of the 1987-D
cent show any smearing.
The most likely hypothesis involves the cent hitching a ride on
the hammer die. I suspect that the newly struck coin clung to the face
of the hammer die as the latter bounced up and shifted northward
(obverse perspective). When the die and its attached coin descended,
the design rim of the latter touched down on the field portion of the
anvil die. While the hammer die was in mid-bounce, the anvil die was
rising up through the collar so as to bring the (now absent) coin in
line with the ejection mechanism.
This may be why the opposite pole of the descending coin was not
blocked or damaged by the upper surface of the collar.
This hitherto unforeseen mechanism opens up the possibility of
more extreme cases of rim-restricted design duplication being found on
the face struck by the anvil die. If you do find a coin with
extensive, raised letter traces on the rim struck by the anvil die,
please let me know.
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