Toning is character. Corrosion is damage. Learn the difference before you pay a premium for either.
Signs of stable toning (character)
- Light, even toning with luster still visible underneath.
- Color that sits on the surface without texture change.
Signs of environmental damage
- Dark, crusty, or pitted surfaces — corrosion eating into the metal.
- PVC green residue — soft green film from old flips; it keeps eating if left alone.
- Spots, streaks, and fingerprint etching — oils burned permanently into the surface.
- Sandpaper texture — the surface is gone, not toned.
The photo trap
Corrosion photographs better than it looks in hand. Assume the worst the image supports, then assume a little worse.
A photograph can inform a decision, but it cannot authenticate or certify a coin.