Collectors commonly put hinges on the backs of mint stamps–sometimes even gluing them into books. This was considered acceptable 100 years ago too, but no stamp collector is confused about the fact that these hinge marks are deleterious.

Coins gain an unsightly oxidation from being improperly exposed to oxygen, moisture, and acids. This is the reason no one stores their coins–Gold, Silver, or Copper, in this manner for many years now. We buy Dansco albums with acid free surfaces and keep them in protective sleeves.

To this collector, the general aesthetic needs to be applied to coins, as it is to most other art forms. We do not like a bleached white 100 year-old parchment, but neither do we like one covered in charcoal. To use Mr. Reynold’s analogy, there are many situations were both antique furniture and documents, are mended, patched, refinished, etc–and it if is done tastefully, by people who are professionals at it, and only where it makes an aesthetic improvement–we accept the emendation.

Coins should be treated no differently. I don’t like a bright-white Barber half dollar either–but even that is preferrable to one which shows grotesque, heavy layers of oxidation from what would be uniformly ackowledged today as mis-handling.

And many coins which were cleaned decades ago, have reaquired an antique patina which is entirely attractive–either under a loop or not.