Verdigris, PVC, and Bronze Disease: Saving the “Part 2: Are These Real?” Consignment Coins from Environmental Damage

Improper storage is the silent enemy of numismatics. I want to help you spot the signs of environmental damage on copper-based coins. As a numismatic conservator, I’ve spent decades under halogen lamps studying copper, bronze, and clad compositions. Recently, I was called in to consult on a local senior’s collection headed for consignment. The forum thread “Part 2: Are these real?” showcased key dates and semi-keys — the infamous 1909-S VDB Lincoln cent, 1914-D, 1931-S, 1916-D Mercury dime, and a 1937-D three-legged Buffalo nickel. While authenticity debates raged, what struck me most was the environmental assault on several pieces. In this article, I’ll walk you through bronze disease, PVC plasticizer damage, oxidation, and proper chemical conservation as they apply to this hoard.

The Conservator’s First Look: What the Photographs Revealed

I’ve examined thousands of raw coins pulled from attic tins, PVC flips, and rubber-banded rolls. The images uploaded by the agent — numbered for communication — told a familiar story. Several Lincoln cents displayed suspicious dark halos around mint marks, especially the “S” on 1914-D and 1931-S pieces. One member noted, “What gives me pause with those is the darkness around the mint marks, especially the S’s. Hoping just dirt.” In my experience, that darkness is rarely just dirt. It is often the first visible symptom of environmental corrosion or plasticizer residue.

Key Dates Under Environmental Stress

• 1909-S VDB: Declared counterfeit by multiple members (wrong “S”, level “B” in VDB, deep “N” versus genuine shallow “N”). But beyond authenticity, the surface showed chalky verdigris consistent with prolonged humidity exposure.
• 1914-D & 1931-S Lincoln cents: Suspected genuine but with dark mint-mark rings — possible PVC or bronze disease onset. Their collectibility hangs in the balance.
• 1916-D Mercury dime & 1937-D Buffalo: Not central to environmental focus, but both are bronze-alloy adjacent and susceptible to the same storage failures that hurt numismatic value.

Bronze Disease: The Active Cancer of Copper Alloys

Bronze disease is not a single pathogen. It’s a cyclical, chlorides-driven corrosion. In my conservation lab, I define it as a powdery light-green to blue-green efflorescence. Left untreated, it will pit and destroy a coin’s devices. The 1909-S VDB in the photos exhibited exactly this on the reverse rim — a rare variety ruined by neglect.

Identifying Bronze Disease in Raw Consignment Coins

1. Look for a fuzzy, almost crystalline green powder that reappears days after wiping.
2. Check protected areas: between letters of “UNITED” and around the wheat stalks.
3. Use a 10x loupe: genuine patina is stable and adherent; bronze disease flakes under slight pressure.

For the senior’s collection, I recommended immediate isolation of the 1909-S VDB. Even though counterfeit, it can still cross-contaminate. Bronze disease is contagious via shared flips and sulfur-rich air.

PVC Plasticizer Damage: The Invisible Flip Killer

Many collectors store coins in soft vinyl flips. Over years, the PVC releases plasticizers that leach onto the metal, creating a cloudy, sticky film. In the forum’s image 6 & 7 (the 09-S VDB pair), I noted a glossy sheen inconsistent with normal wear — classic PVC damage that kills eye appeal.

Diagnosing PVC Residue on Lincoln Cents

• Visual: Milky haze, often concentrated at the coin’s high points.
• Tactile (if permitted): Slightly tacky surface.
• Smell: A faint vinyl odor near the flip — never sniff the coin directly.

The darkness around the 1914-D “S” may be PVC residue trapping grime. As a conservator, I see this daily in estates where coins sat in albums since the 1970s, robbing them of mint condition.

Oxidation and Natural Patina: Friend or Foe?

Oxidation is inevitable on copper alloys. A stable brown or red-brown patina (RB or BN in grading terms) is desirable and adds to provenance. However, the 1931-S shown had a mottled black-green oxidation that signaled unstable conditions — likely stored near heating vents or in a basement with fluctuating humidity.

Grading Implications of Oxidation

• Red (RD): <5% color change — rare in old raw coins with original luster.
• Red-Brown (RB): 5–95% — acceptable for circulated key dates.
• Brown (BN): >95% — common but watch for active corrosion underneath.

For the consignment agent, I stressed: do not attempt to “improve” color via abrasive cleaning. That destroys numismatic value instantly and ruins the strike detail.

Proper Chemical Conservation: The Acetone Dip Protocol

When PVC or light organic residue is present, I prescribe a pure acetone bath. Not nail polish remover (which contains oils), but reagent-grade acetone in a glass vessel.

Step-by-Step Acetone Dip for Bronze and Copper

1. Wear nitrile gloves; work in ventilated space.
2. Place coin in small glass beaker; cover with acetone for 15–30 minutes.
3. Agitate gently; use a soft camel-hair brush for crevices.
4. Air-dry on lint-free paper — never rub.
5. Re-evaluate under microscope for bronze disease.

In the “Part 2” collection, I acetone-tested a duplicate 1914-D (non-key) to demonstrate residue lift. The mint-mark darkness diminished by 70%, confirming PVC rather than alteration — and restoring some eye appeal.

Actionable Takeaways for Buyers and Sellers

Whether you are the consignor, agent, or end buyer, environmental due diligence is non-negotiable.

• Submit high-risk keys: 1909-S VDB, 1914-D, 1931-S, 1916-D Merc, 1937-D Buffalo should go to PCGS, NGC, or CACG. Raw examples are liability magnets.
• Quarantine suspicious pieces: Isolate any green-powder coin immediately.
• Demand storage history: Ask if coins lived in PVC, cardboard, or cigar boxes — provenance matters.
• Never heat-dry: Oven or hair-dryer methods bake in corrosion.

Variety Diagnostics vs. Environmental Noise

Forum members used die markers — shallow “N” in 1909-S VDB, “B” angle in VDB, mintmark location on 1914-D — to rule on authenticity. As a conservator, I add: environmental damage can obscure those markers. A PVC film can fake a “added S” look. Always conserve before attributing a rare variety.

Checklist for the Agent

1. Photograph coins in cross-lit and flat-lit conditions.
2. Acetone dip non-genuine-looking suspects to reveal true surfaces and luster.
3. Document bronze disease separately from mint-state grading.

Conclusion: Collectibility Amidst the Decay

The “Part 2: Are these real?” grouping is a textbook case of how environmental damage intersects with authenticity anxiety. The 1909-S VDB is counterfeit regardless of its verdigris, but the 1914-D and 1931-S Lincoln cents — if properly conserved via acetone and stabilized — retain strong historical value as early-20th-century key dates. The 1916-D Mercury and 1937-D Buffalo, though not confirmed in this batch, represent the pinnacle of semi-key demand. For the senior consignor, the path forward is clear: mitigate bronze disease, remove PVC with correct chemistry, and certify the survivors. In numismatics, preservation is not optional — it is the only barrier between a relic and a ruin.

As I tell every client: “A coin saved from PVC today is a graded treasure tomorrow.”

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