Preserving Your Treasure: Expert Conservation Tips for Shipwreck Gold Coins

The Collector’s Responsibility

I’ve seen too many valuable pieces ruined by improper cleaning or storage. Here’s how to keep this safe for the next generation.

Understanding Your SS Central America $20 Gold Piece

The 1857-S $20 Liberty Head Double Eagle from the SS Central America represents not just a significant numismatic treasure but a piece of American maritime history. This coin, graded MS63 by PCGS, survived over a century underwater before being recovered from the famous “Ship of Gold.”

Historical Context and Metal Composition

The SS Central America sank in September 1857 carrying approximately 30,000 pounds of gold from the California Gold Rush. The 1857-S $20 gold piece contains 90% gold and 10% copper alloy, making it particularly susceptible to specific types of deterioration. The coin’s composition creates a unique preservation challenge that requires specialized care.

The Toning Dilemma: Beauty or Blight?

One of the most debated topics in shipwreck coin preservation is toning. Unlike terrestrial coins that develop toning from environmental exposure over decades, shipwreck coins often exhibit toning from their prolonged immersion in saltwater and subsequent recovery processes.

Natural vs. Artificial Toning

Natural toning on shipwreck coins typically appears as subtle golden hues, sometimes with hints of blue or purple iridescence. This toning is generally considered desirable and should be preserved. Artificial toning, often resulting from improper cleaning or chemical treatments, can appear harsh or unnatural and may actually decrease the coin’s value.

“The toning on a properly preserved shipwreck coin tells the story of its journey. Removing it is like erasing history.” – Conservation Expert

Oxidation: The Silent Destroyer

Oxidation poses a significant threat to gold coins, particularly those recovered from marine environments. While gold itself doesn’t oxidize easily, the copper alloy in your $20 piece makes it vulnerable to several forms of deterioration.

Types of Oxidation to Watch For

Surface oxidation appears as discoloration or pitting on the coin’s surface. Copper spotting manifests as reddish or brown spots where the copper content is more concentrated. Environmental oxidation occurs when coins are exposed to pollutants, humidity, or improper storage materials.

PVC Damage: The Hidden Threat

Polyvinyl chloride (PVC) damage is one of the most common and irreversible forms of damage to coins. PVC is found in many older plastic holders, flips, and storage containers. When exposed to heat or moisture, PVC can break down and release acidic gases that adhere to the coin’s surface.

Identifying PVC Damage

PVC damage typically appears as a slimy green or oily residue on the coin’s surface. In advanced stages, it can cause irreversible surface etching and permanent discoloration. The damage is often most visible in recessed areas of the coin’s design.

Proper Holders: The First Line of Defense

Proper storage is crucial for preserving your SS Central America treasure. The right holder not only protects the coin from physical damage but also creates a stable microenvironment that prevents deterioration.

Recommended Storage Solutions

Air-Tite holders provide excellent protection and are made from inert materials that won’t react with your coin. Intercept Shield holders offer additional protection against atmospheric pollutants. PCGS or NGC certified holders are ideal as they provide both physical protection and authentication.

Materials to Avoid

Avoid PVC-based holders, paper envelopes, and any storage solution containing sulfur or other reactive chemicals. Never store coins in regular plastic bags or containers not specifically designed for numismatic preservation.

To Clean or Not to Clean: The Eternal Question

When it comes to shipwreck gold coins, the answer is almost always: do not clean. Professional conservationists and numismatists overwhelmingly agree that cleaning shipwreck coins can significantly reduce their value and historical integrity.

The Risks of Cleaning

Cleaning can remove the natural patina that developed during the coin’s underwater journey. It can also cause microscopic scratches that are visible under magnification and reduce the coin’s grade. Chemical cleaning can leave residues that continue to damage the coin over time.

When Professional Conservation is Necessary

In rare cases where a coin has active corrosion or harmful deposits, professional conservation may be warranted. This should only be performed by experts specializing in shipwreck artifacts who understand the unique chemistry of marine-recovered treasures.

Environmental Control: Creating the Perfect Storage Environment

Even with proper holders, environmental factors can affect your coin’s preservation. Maintaining stable conditions is essential for long-term conservation.

Temperature and Humidity Control

Ideal storage conditions include temperatures between 60-70°F (15-21°C) and relative humidity below 50%. Avoid storing coins in basements, attics, or areas prone to temperature fluctuations or moisture.

Light Exposure

Prolonged exposure to direct sunlight or UV light can accelerate toning and potentially damage the coin’s surface. Store your collection in a dark or low-light environment, and avoid displaying coins under intense lighting for extended periods.

Documentation and Insurance

Proper documentation is an often-overlooked aspect of coin preservation. Maintain detailed records of your coin’s provenance, grading information, and any conservation work performed.

Creating a Conservation Log

Document the coin’s condition when acquired, including high-resolution photographs. Record any changes in appearance over time and note the storage conditions and materials used. This information is invaluable for insurance purposes and potential future sales.

Regular Inspection and Maintenance

Even with perfect storage, regular inspection is crucial for early detection of potential problems. Establish a routine inspection schedule to check for signs of deterioration.

Inspection Protocol

Examine your coin under proper lighting with magnification. Look for changes in toning, signs of spotting, or any residue on the holder’s interior. Check that seals remain intact and that no moisture has entered the holder.

The Future of Your Treasure

Your 1857-S SS Central America $20 gold piece is more than just a valuable collectible; it’s a tangible piece of American history. By following these conservation guidelines, you’re not just protecting an investment – you’re preserving a story for future generations.

The Manchester show where you acquired this treasure represents the vibrant community of collectors who understand the importance of proper preservation. As you’ve experienced, these regional shows are becoming increasingly important venues for acquiring historically significant pieces like shipwreck gold.

Remember, the goal of conservation isn’t to make a coin look “perfect” or “new,” but to preserve its current state and prevent further deterioration. The slight imperfections and toning on your SS Central America coin are part of its unique story – a story that began over 160 years ago and continues with you as its current steward.

By implementing these preservation techniques, you ensure that this piece of American maritime history will continue to captivate and educate collectors for generations to come. The responsibility of preserving such treasures is significant, but with proper care, your SS Central America $20 gold piece will remain a highlight of your collection and a testament to the enduring allure of shipwreck treasure.

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