Collectors' Clearinghouse column from the Jan. 16, 2017, issue of
Numerous past columns have recounted the various ways in which
normally oriented incuse design elements can appear on a coin. For the
uninitiated, these are design elements that face the same way as the
raised design, but are sunken. In most cases, these sunken design
elements are out of position relative to their normal raised counterparts.
A brief review of known causes follows:
(1) Dropped filling (dropped letter, dropped number, and so on). Die
fill (“grease”) accumulates and gets compacted within a die recess to
form a cast. The hardened cast is eventually dislodged and ends up
lying above or below a planchet. The dropped filling is struck into
the planchet and then falls out, leaving behind an incuse impression.
The impression will be normally oriented unless the dropped element
flips over or winds up between the planchet and the opposite die.
(2) Struck through a thin, struck fragment. A thin piece of metal
gets trapped between a die and a planchet, resulting in a uniface
strike. The impact molds the metal to the recesses of the die. If the
fragment is later dislodged and struck into another planchet, it will
leave behind a set of incuse design elements. Once again, those
elements will be normally oriented unless the fragment flips over
before the strike or it winds up trapped between the planchet and the
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(3) Struck through a shifted die cap or detached cap bottom. A
late-stage die cap shifts out of position, or a cap bottom separates
from its wall and moves laterally or rotates. The areas of the cap
that had conformed to the recesses of the die face are slightly
thicker than elsewhere. As a result, when these thicker areas are
forced into a planchet by the impact of the die, they generate a
duplicate set of normally oriented incuse design elements.
(4) Struck through a delaminated coin layer. A thin layer of metal
detaches from the surface of a struck coin. If the layer continues to
face the die that produced its raised design, the layer will generate
a set of normally oriented incuse design elements when it’s struck
into a fresh planchet.
(5) Broken or chipped hub. When the raised details on the face of a
working hub break off, the fracture plane is sometimes located just
below the surrounding field. When such a chipped hub is pressed into a
working die, and that working die is then struck into a planchet, the
chipped component ends up slightly recessed relative to the
surrounding field. Naturally, the incuse component occupies its normal
position within the design.
(6) Die deterioration. Some forms of die wear can generate
incomplete incuse elements (outlines, for the most part) that lie
alongside their normal raised counterparts.
A different scenario
A few weeks ago I came across an extensive set of normally oriented
incuse design elements that cannot be traced to any of the scenarios
listed above. They are found on the obverse face of a 2010 Pakistan
2-rupee coin. A good portion of the Urdu script is incuse instead of
raised, with these incuse letters occupying their normal positions
relative to the flanking raised letters.
This is clearly not the result of a chipped hub. The edges of the
incuse elements are too soft. Furthermore, a chipped hub is unlikely
to involve a chain of unconnected letters and is equally unlikely to
involve the complete loss of each letter.
I believe that these incuse letters represent the impressions of die
fill that rose out of the letter recesses, above the level of the
die’s field. This normally shouldn’t happen. When a die recess is
completely filled, any additional “grease” will flow over onto the
field, obscuring the edges of the design.
I suspect that in this case, the die fill expanded like warm dough
rising out of a muffin pan. Dies can get rather hot during use, and it
would appear that this material was prone to heat expansion.
One feature that supports this scenario appears at the right end of
the arc of faint script. Here one character and part of another are
actually raised. The die fill didn’t completely fill the corresponding
recesses and instead generated a normal-looking “filled die” error.
As to what this novel type of “struck-through” error should be
called, I suggest the term “bulging die filling.”