Cleaning a coin can take 50–90% of its value off in about thirty seconds

What cleaning actually does

Here's the part that makes it so cruel. The coin usually looks better to you afterwards. Brighter, sharper, more like money. What you've removed is the surface the coin spent a century acquiring, and with it the thin film of oxidation collectors call toning. Under a loupe the difference is not subtle. It's a field of fine hairlines running in whatever direction your cloth went, and it reads as damage to anyone who grades coins for a living.

Grading services list cleaning as a reason to refuse a numeric grade altogether. A coin that would have graded and sold as a collectible comes back in a holder marked as damaged, which moves it into a different market at a fraction of the price. That's the mechanism behind the 50–90% figure. It isn't a penalty someone chose to apply. It's what the coin is now worth to the people who buy coins.

The coin looks better and is worth less. Both things are true at once, and that's why this mistake keeps happening.The first line of every HeirLoupe coin report

Cleaning is not conservation

These get conflated constantly, and the difference is worth a lot of money.

Dirt versus toning

Toning is the colour a coin develops over decades — grey, gold, blue, sometimes a rainbow across the field. It's oxidation, it's original, and on some coins it adds a premium rather than subtracting one. Dirt sits on top. Toning is part of the coin. If you can't tell which you're looking at, that alone is the reason to leave it alone, and it's a reasonable thing not to know — we can't always tell from a photograph either, and we say so when we can't.

The do-not list for coins

Three rules. They cover most of the damage we see in inherited collections, and every one of them is something people do while trying to be helpful.

• Do not clean the coins. Any of them. Ever. Cleaning leaves microscopic scratches that graders detect instantly. A cleaned coin routinely loses 50–90% of its value, and it cannot be undone. This is the single most expensive mistake heirs make.
• Do not remove coins from sealed holders or original mint packaging. The packaging is part of the provenance, and proof sets in their original cases are worth more intact than the coins are loose. Photograph through the plastic.
• Do not sell to the first buyer who offers for the whole lot. A sight-unseen offer on an entire collection is a bet that there's something good in it. That bet is being made against you. The real arithmetic on dealers, auction houses and eBay is worth ten minutes before anyone writes a cheque.

The same mistake in six other boxes

Coins get the attention because the loss is so steep. But every category in an inherited estate has one move that can't be walked back, and in most of them it's also a cleaning instinct.

If the boxes in your garage cover more than one of these, start with the first-week checklist rather than opening anything.

What the mistake costs

We can't tell you what your coins are worth in a paragraph, and anyone who does is guessing. What we can do is show you the shape of the risk.

Say a box holds two hundred common circulated coins and three that matter. That's the usual pattern — most inherited coin collections are mainly common coinage worth close to face value, with a small number of genuinely interesting pieces mixed in. The three that matter might be key dates: a 1909-S VDB cent, a 1893-S Morgan dollar, a 1916-D Mercury dime. An afternoon with a polishing cloth treats all two hundred and three identically. The two hundred lose nothing, because they were worth close to face value either way. The three lose most of what they were worth.

We're deliberately not printing a dollar figure for those coins here. Their value swings on wear at the highest points, on the mint mark, on whether the surfaces are original — things nobody can read off a blog post, and things we're careful about even with a photograph in front of us. What an inherited coin collection is actually worth goes through what drives the number.

Checking costs less than the mistake by a wide margin. A free first look takes five photos and tells you whether anything in the box deserves a closer examination. The full report is $39 for up to 200 photos. What each tier covers is a short page. We charge a flat fee and we never buy, never sell and never take a percentage, so we have nothing to gain from telling you the box is worth less or more than it is.

What to do instead, in order

1. Put the cleaning supplies away

   Close the box. Nothing in it is getting worse this week. Damp and heat do real damage over months, so move it out of the garage or the attic, but that's the only urgency here.

2. Leave everything in its holder

   Sealed flips, mint cases, proof sets, cardboard 2x2s — all of it stays shut. Photograph through the plastic. Glare is easier to work around than a coin you've already taken out and handled.

3. Photograph both sides in daylight

   Diffuse daylight near a window, not direct sun and not flash. Glare hides exactly the detail that identifies a coin. Fill the frame with one coin at a time for anything that looks unusual, and get both sides. The date and the small letter next to it — the mint mark, usually S, D, CC or O — matter more than almost anything else.

4. Set aside anything pre-1965

   US dimes, quarters and half dollars dated 1964 or earlier are 90% silver, which makes them worth many times face value as metal alone before anyone talks about collector value. They're worth separating out and photographing individually.

5. Get a read before anyone makes an offer

   Knowing roughly what's in the box changes every conversation that follows. A free first look on five photos is enough to tell you whether the box is worth a full examination. How the examination works explains the three passes and why every figure comes back as a range.

When it genuinely doesn't matter

Plenty of coins are worth face value and always will be. A jar of post-1982 cents, a handful of foreign coins from a holiday, a modern quarter with a scratch already across the face — cleaning those changes nothing, because there was nothing to lose. If you want them shiny for a grandchild's collection, go ahead.

The problem is that you can't reliably tell which jar you're holding. Key dates look like ordinary coins to almost everyone. A 1916-D dime sits in a jar looking exactly like a dime. That's the whole reason to check first, and it's also why this guide is wrong for one group of people: if you already know how to read a mint mark and grade a surface, you don't need us. Nothing here will be news to you.

This is an informational estimate from photographs, not a certified appraisal. We tell you what is worth paying an appraiser to look at — we have no interest in buying anything you own. Values are always given as ranges, and where a photograph can't settle it, the report says “worth a professional look” rather than inventing a figure.