Among the most enduringly popular striking errors is the
double-denomination error. Such errors occur when a coin of one
denomination is struck a second time with the design of another
denomination. Familiar examples include a cent struck on a dime and a
5-cent coin struck on a cent.
Far more exotic combinations certainly have occurred at the U.S.
Mint facilities. Dual country, double-denomination errors comprise a
small but distinguished subset. They are an inevitable consequence of
the U.S. Mint’s long involvement in striking coins for other countries.
I recently came across a very peculiar example of such an error on
the auction site eBay. It consists of a Kennedy half dollar design
struck over a 30 percent off-center Philippine 10-centavo coin. Quite
of bit of the host coin’s design is preserved.
This example was part of a consignment of Philippine coins offered
by The Private Collector Group, an outfit that also features
continuous auctions of coins and other collectibles on its Web site,
When I spied the coin in its Numismatic Guaranty Corp. slab, I
quickly determined that the label was not quite accurate. While NGC
correctly identified the country, denomination and the error affecting
the host coin, the date the grading firm assigned to it (1988) was
wildly inaccurate. A little bit of research would have shown that the
design of the host coin was last used in 1966. A little more research
would have revealed that the U.S. Mint last struck this design on
behalf of the Philippines in 1963. Finally, this denomination
underwent a name change in 1967, rechristened as the 10 sentimos.
The reverse face of the host coin features the allegorical figure
of liberty standing to the left of a smoking volcano, Mount Mayon.
Above her head is the denomination spelled out — ten centavos. The
date appears at the bottom of the design.
The obverse of the coin has the national shield in the center.
Just below the shield is a ribbon inscribed republic of the
philippines. Surrounding shield and ribbon is the legend central bank
of the philippines.
The date of the host coin crosses Kennedy’s cheek bone and nose.
The first two digits are clear, while the last two digits are quite
faint. A careful examination under a microscope did reveal the date to
be 1963. This probably means that the half dollar design was struck in 1964.
Probably not assisted
One could be forgiven in thinking that this is some kind of
assisted error. After all, it seems inconceivable that an error coin
from the previous year could make its way to a half dollar press
unassisted. However, there is at least one scenario that makes this
event not only possible, but quite reasonable.
Undersized, oversized and misshapen error coins are often
intercepted by a riddler, a screening device that leaves oversized
coins above a screen with holes that admit coins of normal diameter. A
second screen with holes too small for a normal coin filters out
undersized error coins. Coins separated in this fashion are
automatically routed to a container that contains an accumulation of
When the container becomes full, its contents must be transported
to a furnace for melting — a job done in-house during the time period
in which this coin would have been struck. Until the late 1990s, all
manner of material was moved around the Mint in all-purpose tote bins.
This includes blanks, planchets, normal coins, error coins and waste
material like chopped-up strip.
It is entirely possible that this off-center Philippine 10-centavo
coin remained behind when the contents of a tote bin were emptied. It
was then presumably buried under a subsequent load of half dollar planchets.
This is not the only double-denomination error involving an
abnormal host coin. Indirect evidence of such a coin can be found at
http://kennedyhalfdollar.com/, a site constructed
by Ken Glickman, called The Home of the Kennedy Half Dollar.
One page features a 1981 Kennedy half dollar that has on its
obverse face a full brockage of the reverse design of an error quarter dollar.
From the looks of it, the coin that generated the incuse,
mirror-image impression was a quarter dollar struck slightly
off-center on a 5-cent planchet. Glickman found his coin in a roll
obtained from his local bank, so there’s no doubt in my mind that it
resulted from an accidental event. The scenario I proposed for the
half dollar/10-centavo coin error would be equally applicable to
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