There are a number of aspects and nuances to this topic, and tools, techniques and attitudes have changed over the years as well, leaving behind a treacherous landscape.

In numismatics, the advice to a non-collector is always to never attempt to clean or otherwise improve the appearance of a coin. This is because doing it right takes skill and experience, and most amateur attempts, however well-meaning, are ham-handed and result in damaged coins.

"Doing it right" is one of the nuances, as are "well-meaning" and "damaged". Let's start with damage, because it's fundamentally linked to marketplace value.

Damage: Holes, dings, dirt, dents and scratches are among the worst forms of damage to a coin. For paper money the list would include holes, dirt, folds/creases, and graffiti. There's almost nothing to like about any form of damage, and damage decreases the value to a collector (although there are some rare exceptions such as a famous person's signature, a famous collector's identification mark or even a famous bullet hole).

Wear and toning are forms of damage as well, and there are books and whole industries built around the topic. The more wear, the less desirable the piece. As an engineer I'd like to think that damage, wear and toning are absolute and easy to measure and to some extent they are, but beauty is in the eye of the beholder and there is room for interpretation even here, especially with toning. One man's gorgeous toning is another's hideous discoloration. Today's "Numismatic Nuggets" column illustrates what I think is a nicely toned piece. Was it toned artificially? Does it matter?

Skill: Rubbing silver coins with a baking soda paste will make them look nice and shiny, but it will also inflict great damage on the coin's surfaces. "Whizzing" is another old practice of buffing a coin that leaves a multitude of traces on the coin. While improving one aspect of the coin, they inflict great damage on other aspects. By further damaging the coin these attempts reduce value. "Doing it right" is important.

But what if the work is so good that the coin ends up in state where no damage is added and none is visible or detectable? If the earlier damage is removed without a trace, is the piece now more desirable? Is it worth more than before? Well, that can be a tricky question, too. Your coin has been "doctored". My coin has been "carefully conserved".

Consider paper money. Because banknotes have serial numbers it's possible to trace individual notes over time. Today's nice, clean, flat, crisp note had two smudges, a hole and four creases when it was sold ten years ago. Did it magically heal itself in a safe deposit box down the road from a nuclear waste dump? Or did someone carefully close the hole and clean and iron the note before putting it up for resale? Is the note worth more, less, or the same? Is that doctoring or conservation?

Intent: This is the "well-meaning" part. If repairs and retoning are fully disclosed with no attempt to deceive, then potential buyers have the information they need to decide how much a piece is worth to them. I might pay more for a properly conserved piece than an unconserved one. Would I pay as much as I would for a completely original piece that never required conservation? Maybe, maybe not. OK - probably not. But let me decide that.

And of course, there is the routine conservation that is not repair at all but simply the removal of dirt and contaminants that could cause damage in the future. That's simply good stewardship. As Alan V. Weinberg stated (see the 2013 article linked below): "The "doctored" appellation should apply exclusively to defects concealed by a process in an attempt to increase value and deceive a buyer, not to merely preserve condition."

It's a complicated topic, and one where opinions and practices change and evolve over time. See the E-Sylum article about the PCGS "Sniffer" system that was rolled out to detect traces of foreign substances on coins submitted for authentication. The referenced video has since been taken down. The E-Sylum screen captures may be the only remaining trace of this technology.

I ran my thoughts past E-Sylum regulars Joel Orosz and Len Augsburger, and they shared these observations. Thanks. -Editor