Is Your Shipwreck Coin Slab Authentic? A Collector’s Guide to Authentication

Historical Significance

The allure of shipwreck coins has captivated collectors for decades. These coins, recovered from maritime disasters, carry both historical significance and the romance of treasure hunting. The slabbed shipwreck coins you’re examining represent a unique intersection of numismatics and maritime archaeology, making authentication particularly important for serious collectors.

Authentication Guide: Key Diagnostic Points

With counterfeits flooding the market, knowing the specific diagnostic points for these shipwreck slabs is critical. Authentication requires attention to multiple factors that distinguish genuine specimens from sophisticated forgeries.

Weight Verification

Authentic shipwreck coins in slabs should maintain their original weight specifications. Most recovered silver coins from historic shipwrecks should weigh between 26.5 and 27.5 grams, depending on their specific type and origin. Deviations of more than 0.5 grams from documented specifications warrant closer examination. When weighing, ensure your scale is properly calibrated and use a non-magnetic weighing dish.

Magnetic Properties Testing

A fundamental test for any suspected shipwreck coin involves magnetic properties. Genuine silver and gold coins should be non-magnetic. If your coin exhibits any magnetic attraction, this is an immediate red flag. Some sophisticated counterfeits use magnetic steel cores with precious metal plating, so even slight magnetic properties indicate potential forgery.

Die Markers and Design Details

Authentic shipwreck coins display specific die markers that counterfeiters often miss. Examine the coin under 10x magnification for these critical details:

• Sharpness of detail in high-relief areas
• Consistency of edge reeding or lettering
• Surface texture matching documented examples
• Patina patterns consistent with saltwater exposure

Pay special attention to mint marks and date positions, as these are common areas where counterfeiters make errors. The specific shipwreck slab type mentioned in the discussion may have unique die characteristics worth documenting.

Common Fakes to Watch For

The market has seen several categories of shipwreck coin fakes:

Modern reproductions using incorrect metal compositions, artificially aged coins with fabricated provenance, and sophisticated counterfeits using genuine coin casts with altered dates or mint marks.

Be particularly wary of coins claiming extraordinary provenance without documentation. Authentic shipwreck coins typically come with certificates of authenticity and detailed recovery information.

Testing Methods

Beyond basic weight and magnetic tests, consider these additional authentication methods:

• Specific gravity test using water displacement
• Sigma or XRF testing for metal composition
• Microscopic examination of surface crystallization patterns
• UV light examination for modern tool marks

The specific slab type discussed appears to be larger than standard coin slabs, similar to ATB (America the Beautiful) quarter slabs. This size difference is important for both authentication and storage considerations.

Storage Solutions for Oversized Slabs

The forum discussion reveals practical storage solutions for these unique slabs. NGC produced specialized boxes for this size – one holding 7 coins and another holding 12. If original boxes are unavailable, collectors have improvised with:

• CD cases (as mentioned in the discussion)
• Laying them flat in Intercept boxes with standard slabs
• DIY storage solutions

Proper storage not only protects your investment but can also help maintain the slab’s integrity, which is crucial for authentication purposes.

Conclusion

Authenticating shipwreck coins in these oversized slabs requires a multi-faceted approach combining physical testing, visual examination, and provenance verification. The investment in proper authentication tools and knowledge pays dividends in protecting your collection from sophisticated counterfeits. Whether you’re a seasoned collector or new to shipwreck coins, understanding these diagnostic points will help you make informed decisions and preserve the integrity of this fascinating numismatic specialty.

Related Resources

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