I’ve always assumed that a double-denomination error would
necessarily also be a wrong planchet error. After all, I’m not aware
of any nation that uses the exact same planchet for two or more of its
Even among dual-country, double-denomination errors, this rule has
generally held, since each nation establishes its own coinage
specifications, and these are unlikely to match those of any other nation.
Sometimes by intention
I will concede that certain foreign coins are struck on planchets
identical to those of another denomination that happens to belong to
the nation that strikes both. From 1968 to 1984, the U.S. Mint struck
(with periodic interruptions) Panamanian tenth-, quarter- and
half-balboa coins on copper-nickel clad planchets that were
respectively identical to domestic dimes, quarter dollars, and half dollars.
Had any of these U.S. designs been struck over a Panamanian coin
of identical specifications, you would naturally have a
double-denomination error without any change in composition, diameter,
While I’m not aware of any such errors, there are a number of
Panamanian 1982 half balboas struck over earlier Kennedy half dollars.
In an online article, Ken Glickman provides persuasive evidence that
all were intentionally struck (http://kennedyhalfdollar.com/about-halves/blue-balboa-kennedy.html).
Recently, error dealer Fred Weinberg came up with a pair of
dual-country, double-denomination errors in which the final strike was
on its proper planchet. But the route taken was quite different from
the one just described. In each case, the host coin happened to be an
off-metal strike on a planchet appropriate for the final strike.
The first coin presented here is a 1983 Canadian cent struck over
an Israel 10 shekels that in turn was struck on a Canadian cent
planchet. This particular 10-shekel design, which features an ancient
galley on the obverse face, was produced in the years 1982 to 1985.
Slightly larger than a U.S. quarter dollar, this solid copper-nickel
coin was struck at the Royal Canadian Mint.
The second coin is a 1982 Costa Rican 25-centimo piece struck over
an Israel 10-shekel coin that was in turn struck on a Costa Rican
25-centimo planchet. Composed of aluminum, the Costa Rican 25-centimo
coin of this time period is slightly smaller than a U.S. quarter
dollar and was also struck at the Royal Canadian Mint. This is the
only dual-country, double-denomination error I’m aware of in which
neither strike belongs to the nation actually contracted to do the striking.
Weinberg verified the weights of both planchets before encapsulation.
Likely intentional errors
I strongly suspect that both coins are intentional errors. It’s
highly unlikely that a planchet intended for one denomination would be
struck by another denomination and then return to the correct
production stream in advance of the final strike.
It’s also probably no accident that the Costa Rican 25-centimo
strike (and by the looks of it, the Canadian cent strike as well) were
struck in-collar. In both coins, the strike of the Israel 10-shekel
coin appears to have been of respectable strength. This should have
caused the planchets to expand beyond the diameter of a Canadian cent
collar and a Costa Rican 25-centimo coin collar, respectively.
Consequently, the final strike in each case should have been a broadstrike.
I strongly suspect that, after the Israel strike, each off-metal
coin was rolled and squeezed to a smaller diameter that would once
again fit into the collar chosen for the final strike. To accomplish
this, it’s possible that each off-metal Israel coin was fed into the
upset mill appropriate for the planchet it was struck on. By this
means, the 10-shekel coin struck on the Canadian cent planchet would
have had its diameter reduced to something less than 19.1 millimeters
(the diameter of a normal Canadian cent) and the 10-shekel piece
struck on the Costa Rican 25-centimo planchet would have had its
diameter reduced to slightly less than 22 millimeters (the diameter of
a normal 25-centimo piece).
According to the eBay auction descriptions under which these coins
appeared, each example was sold to Weinberg by the son of an Israel
Mint director. This detail adds even more weight to the argument that
these are intentional errors.
When a double-denomination coin is released through normal
channels, it is bundled together with other coins that carry the same
design as the final strike. So the Canadian error coin should have
been discovered in Canada amidst a shipment of Canadian cents and the
Costa Rican error coin should have been discovered in Costa Rica
amidst a shipment of Costa Rican 25-centimo coins.
The fact that both coins ended up in the hands of an Israel Mint
director suggests that they were purposely shipped directly to Israel
or even hand-carried across the Atlantic.
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