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The Bullion Blog

Shipwrecks & Coin Grading: Insights from the Numismatic Guaranty Corporation

July 17, 2022

It’s not uncommon for coins to sustain damage when lost at sea for an extended period of time, but the coins recovered from the S.S. Central America were in surprisingly good condition. This can be attributed to the fact that they were made of gold, which is highly resistant to corrosion. The Numismatic Guaranty Company (NGC) was able to grade one of the 1857-S $20 gold coins recovered from the shipwreck as NGC MS-67 PL, making it the finest known Prooflike example of the coin. Four of the other coins received an NGC MS-67+, meaning they were almost at the level of NGC MS-68.

The recovery of these coins brought an end to a mystery that had captivated treasure hunters for years. The S.S. Central America was a steamship that sunk in 1857, carrying with it a wealth of gold from the California Gold Rush. When the final unopened cargo from the ship was revealed to the public in February 2022, it contained a number of these gold coins in excellent condition despite being submerged in seawater for over a century.


Did the saltwater damage the coins?

Saltwater can be damaging to coins made of certain metals, such as silver and copper, as they are not as resistant to corrosion as gold. However, even gold coins can be affected by other factors in the underwater environment, such as sand and microorganisms attaching themselves to the coin, causing encrustation and potential damage. In the case of the S.S. Central America treasure, the gold coins were protected from these elements by being sealed in a San Francisco Mint Box.


What is the NGC Shipwreck Certification?

Coins that have been recovered from the sea can sometimes show signs of damage caused by saltwater, depending on the type of metal they are made of. Gold is particularly resistant to corrosion from saltwater, which is why the coins recovered from the S.S. Central America were in such good condition after being lost in the ocean for 131 years. Silver and copper coins, on the other hand, are more susceptible to damage from saltwater and can become heavily corroded. In addition to saltwater, coins can also be damaged by sand and microorganisms that attach themselves to the surface.

To address the unique challenges of certifying and grading coins that have spent time underwater, the Numismatic Guaranty Company (NGC) has a division called NGC Shipwreck Certification. This division provides independent assurance of the pedigree of recovered artifacts, evaluates their condition, and assigns a grade. If coins show no signs of having been immersed in water, NGC uses its normal Coin Grading Scale. If the coins show signs of corrosion or other damage, NGC applies its Shipwreck Effect designation, which takes into account the effects of saltwater and other natural elements on the coin. In order to be eligible for Shipwreck Certification, coins must be obtained through non-invasive means and recovered in a way that preserves the history of the wreck.


Grading shipwrecked coins

Numismatic Guaranty Company (NGC) has developed a unique system for grading coins that have been recovered from shipwrecks. The Shipwreck Effect Grading Scale includes six categories, with the highest, A, reserved for coins that show minimal surface disturbance and have superior eye appeal. Lower grades, B through E, reflect increasing levels of corrosion, metal loss, and design disturbance. NGC also assigns a wear or detail grade to Shipwreck Effect coins, ranging from Uncirculated to Good, and provides a Genuine designation when the origin of the coin is documented and confirmed. NGC’s Shipwreck Certification division is the only independent third-party service for shipwreck coin certification and has been entrusted with certifying treasures from several shipwrecks, including the S.S. Republic, 1715 Treasure Fleet, S.S. Pulaski, and S.S. New York.

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