When the unstruck portion of an off-center coin displays an abnormal
surface texture or topography, it can point to subsurface
irregularities, improper planchet preparation, or various external insults.
A particularly dramatic example of an externally generated surface
texture is seen here on an off-center 1965 Lincoln cent. The unstruck portion shows a clear
weave pattern on both faces. All evidence indicates that a layer of
cloth was rolled into both sides of the cent strip, most likely near
the leading edge. A Mint worker was probably protecting his hands from
the hot, sharp edge of the strip while guiding the latter into the
rollers for its final pass. The rag was probably grabbed by the
rollers and dragged into the rolling mill along with the strip. I know
of a second, similar example.
Externally induced textures are more often the result of post-strike
damage but not on the following coin. An undersized (23.54
millimeters), underweight (4.66 grams) 1995-P Washington quarter dollar preserves a fine matte
texture on both faces with marked pitting on the reverse. It suggests
that the planchet was sandblasted, or abraded in a similar fashion
before striking. So much metal was lost around the perimeter that the
copper core is exposed on both faces. The planchet was also rolled and
squeezed in the horizontal plane before striking, relocating metal
from copper core onto the obverse and reverse perimeter. I know of
half a dozen similar quarter dollars from the mid- to late 1990s. The
source of the damage is unknown.
Connect with Coin World:
Mechanical damage is not the only type of external assault that can
alter the surface of a planchet.
Chemical attack seems to be the best explanation for the pitted
surface seen on the unstruck portion of a severely underweight (3.38
grams rather than 5 grams), off-center 5-cent coin. Since the diameter
(20.70 millimeters) is similar to, and the composition (75 percent
copper, 25 percent nickel) identical to, a normal 5-cent planchet, I
would assume that this is how it started out, and that the missing
weight was dissolved away. Perhaps the wrong chemical mixture was used
in the rinse bath after annealing. Many of the pits are filled with a
white substance that is presumably a residue left behind after the
planchet was removed from its harsh immersion.
Get our free report: How to Invest in Rare Coins
Prolonged exposure to excessive heat would best explain the bizarre
appearance of an Uncirculated 5-cent coin struck on a dime-sized
copper-nickel planchet that weighs a mere 1.86 grams. Weakly struck
due to its thinness, it is covered by a rough, brown patina upon which
are scattered small lumps that look like solidified globules of
formerly molten metal. Since they stand above the surface of the
planchet, some of these lumps have been struck in isolation. Although
the appearance of this coin is not typical of improperly annealed
planchets, I don’t know where else besides the annealing oven the
necessary amount of heat would have been generated.
Our final piece — an off-center 1993-P Jefferson 5-cent coin — shows a lumpy surface
texture that at first appears due to a battering but is actually
intrinsic to the planchet. The lumpiness evidently reflects a coarse
and uneven interior micro-structure that rose to the surface when the
planchet was stressed by upsetting and the strike. The lumpiness is
most severe along and just inside the proto-rim and along the external
margin of the off-center strike. I have a second 1993-P 5-cent coin —
an enormous broadstrike — that shows the same pattern of lumpiness
around the edge and the unstruck perimeter.