Inherited a 90% Silver Coin with Green Deposits? What You Need to Know Before Selling It from an Estate

If you’ve just inherited a 90% silver coin with green deposits, your stomach probably dropped. My first instinct when I found a similar piece in my own family’s collection was to take it straight to a local pawn shop. But here’s the thing—taking a rushed approach means you could leave serious money on the table.

When I first started as an estate liquidator, I ran into the same scenario over and over again. Families would inherit a coin collection—sometimes tucked inside a cigar box, a forgotten shoebox, or a safe deposit box—and the very first question they’d ask was about cleaning it. “It’s got this green stuff on it,” they’d say, eyes wide with worry. “Can you just scrub it off before we sell it?” I’ve had this conversation dozens of times, and my answer is always the same: stop. Don’t clean it yet.

The green deposits you see on a 90% silver coin are not what most people assume them to be, and the wrong cleaning approach can permanently destroy the coin’s numismatic value. A piece that might be worth a small fortune in its original patina could easily become a lesser-known, damaged coin if scrubbed the wrong way. Understanding what you’re dealing with is the very first—and most critical—step in estate liquidation.

Understanding What’s Actually on Your Inherited Silver Coin

Let me be precise about the chemistry here, because this matters enormously when you’re deciding how to proceed. A 90% silver coin—like the classic US dimes, quarters, and half dollars minted before 1965, or Canadian silver dollars and British silver pieces—contains 90% silver and 10% copper. That 10% copper is the key to understanding what’s happening on the coin’s surface.

Here’s what the forum discussions among experienced numismatists reveal, and what I’ve confirmed through years of handling inherited collections:

• Verdigris is a copper compound. Let’s talk about verdigris, because it’s the biggest villain in the coin-collecting world when it comes to mint condition. In the strictest chemical sense, verdigris refers to copper salts—basic copper carbonate or copper acetate—formed by a mineral, non-living chemical reaction. It simply cannot develop on pure silver.
• 90% silver coins can develop verdigris-like deposits because the 10% copper content in the alloy provides the substrate for copper salt formation, though under normal environmental circumstances, there is typically not enough copper exposed to produce true verdigris. This is why preserving the original luster and eye appeal is so important.
• What most people call “verdigris” on silver coins is actually PVC residue. Polyvinyl chloride from old coin flips, vinyl holders, or PVC-containing storage materials creates greenish deposits that can be mistaken for corrosion. PVC goo is organic in nature and dissolves readily in acetone—it’s a quick fix that won’t damage your coin’s provenance.
• True verdigris on silver is rare but possible under unusual circumstances, and it cannot be removed with acetone. It requires acidic treatments such as sulfuric-acid-thiourea coin dips or ammonia solutions. If your coin happens to be a rare variety, this is exactly why you must never guess at the cleaning method.

Why does this distinction matter so much for your estate? Because the cleaning method you choose—or that a well-meaning relative chose before handing the collection to you—directly impacts the coin’s collectibility. A coin cleaned with the wrong substance may have its surface damaged, its originality destroyed, and its grade reduced from mint condition to something merely bullion-worth. You don’t want to scrub away a fortune.

Why Professional Appraisal Is the First Step in Estate Liquidation

Before you spend a single dollar on cleaning supplies or consign a single coin to an auction, you need a professional appraisal. I cannot stress this enough. When I handle estate liquidations, I always recommend that clients obtain at least two independent appraisals before any sale proceeds. I’ve seen families rush this step and regret it deeply.

Here is why this step is non-negotiable, particularly from an inheritance tax perspective:

1. IRS Requirements for Estate Taxation. The Internal Revenue Service requires a qualified appraisal for any coin collection included in an estate valued above certain thresholds. The appraisal must be conducted by a certified numismatic appraiser—someone recognized by organizations such as the American Society of Appraisers (ASA) or the International Society of Appraisers (ISA). Without this documentation, you risk either overpaying estate taxes or, worse, facing penalties for underreporting.
2. Establishing Fair Market Value. Fair market value is what a knowledgeable buyer would pay a knowledgeable seller in an arm’s-length transaction. This is not the same as bullion melt value, and it is certainly not the amount a pawn shop will offer you. A professional appraiser will evaluate each coin based on its date, mint mark, grade, strike characteristics, luster, and current market demand. They aren’t just looking at melt value—they are assessing the coin’s true numismatic value and eye appeal.
3. Documenting Condition Before Any Treatment. A qualified appraiser will photograph and document the coin’s current condition, including any surface deposits, natural patina, toning, or corrosion. This creates a baseline record that protects you if a dispute arises later regarding the coin’s condition at the time of sale, ensuring its provenance remains intact.

Actionable takeaway: Before you clean, rub, or treat any coin from an inherited collection, hire a certified numismatic appraiser. The cost—typically $100 to $300 per hour—is a fraction of what you stand to lose if you accidentally strip away the coin’s eye appeal or damage its mint condition.

The Acetone Question: Safe Cleaning for PVC Deposits on 90% Silver

Once you’ve had the coins appraised and documented, you may decide that cleaning is appropriate—particularly if the deposits are PVC residue from old storage materials. Experienced numismatists confirm that 100% acetone is the correct solvent for PVC removal, and I’ve seen it work wonders on inherited collections.

Here is what I’ve learned from handling hundreds of inherited collections and from the expert guidance shared in those discussions:

• Acetone is safe for silver and gold coins. Unlike copper coins, which require oil-based preservatives like Verdicare to prevent further corrosion, silver is a stable metal in environmental conditions and does not need oil-based preservatives after cleaning. This makes it forgiving to work with.
• Use 100% pure acetone, not nail polish remover. Nail polish removers often contain oils, fragrances, and other additives that
  

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