When it comes to shipwrecks, gold coins have it lucky when compared
to silver coins.
Gold is not particularly reactive and many properly conserved gold
coins show virtually no evidence of their shipwreck status. For
example, many of the gold coins from the SS Republic and the SS
Central America were conserved to current market grading
standards and have enjoyed a robust secondary market in the past decade.
Silver coins nearly always show evidence of their time in the sea.
Numismatic Guaranty Corp. has a shipwreck coin
certification program that advertises itself as “the only
independent third-party shipwreck coin certification company providing
professional services for experts and companies specializing in the
field of shipwreck archaeology.”
NGC says that the service provides independent assurance of the
pedigree of recovered artifacts and the service confirms that coins
were recovered in an “archaeologically sound manner” and that the
coins were “conserved by the least invasive means possible to ensure
stability of the artifact surface and long-term preservation.”
NGC has established grading standards for shipwreck effect coins on
an A, B, and C scale for the severity of surface problems resulting
from exposure to saltwater, combined with a details grade to describe
wear on the coin prior to saltwater exposure.
“Shipwreck Effect A” coins exhibit minimal surface disturbance from
saltwater exposure and carry superior eye appeal for a shipwreck
artifact. Coins in the “B” category will have above-average eye
appeal. “C” coins have at least average eye appeal, with moderate
disturbance to the surface, but “accurate attribution and
identification is not hindered by any surface impairment.”
Coins graded with the general “Shipwreck Effect” grade show heavy to
severe disturbance from saltwater exposure, with metal loss affecting
the design. NGC adds, “While accurate identification and attribution
may be possible, it is no longer possible to draw conclusive
determinations about the coin’s surface prior to saltwater exposure.”
But this does not mean that the coins are unattractive.
For example, an 1861-O Seated Liberty half dollar from the SS
Republic graded NGC Shipwreck Effect is identified by its
reverse as an issue struck under the Confederate States of America.
The corrosion is clearly apparent on both sides, though it appears to
have Mint State details. It brought $1,057.50 at a Dec. 6, 2013,
Heritage auction, just over what a solid About Uncirculated 50 example
sold for earlier that year.
While lower-value coins will get a boost from being certified as
coming from a well-known shipwreck, higher-value coins often trade at
a discount to problem-free coins