tarnish in delay of Mint set release
By U.S. Mint
that were detected during the production of
2009-D Lincoln cents at the Denver Mint for the
2009 Uncirculated Mint set have led U.S. Mint
officials to delay release of the set until the
tarnish issues can be remedied.
Sales of United States Mint Uncirculated Coin
Sets will be delayed from the middle of July
until an unspecified date later this year.
A problem with protecting the uncirculated
surfaces of the new Lincoln cent from premature
toning is the cause of the delay.
By law, the four new Lincoln cents in the set
will be made of the same alloy that the first
Lincoln cent was made of in 1909.
That composition, 95 percent copper, 3 percent
zinc and 2 percent tin, Mint technicians have
discovered has "unique tarnish issues."
These tarnish issues are of sufficient severity
that the Mint has acted to delay mint set sales
until they can be resolved.
"Even with normal anti-tarnish treatment," the
problem occurs with the cent's surfaces.
The normal treatment was developed for use on
the copper-coated zinc cents that have been the
standard Mint issue since 1982.
"The pure copper surface is not as susceptible
to tarnish as the bronze alloy." the Mint says.
Even when the Mint achieves a satisfactory
outcome with the new cents, the coins will be
"expected to tarnish more over time than plated
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