Delightful toning like this can be done by resting **FDC coins on chlorinated white paper in sunlight, on a window sill. Keep away from dust by covering with a small glass jar. Enclose in an airtight when ready.
A reasonably safe procedure, but cannot return to original.
I don't do it.
I prefer blast white coins, as near to 'as struck' condition as possible.
Nice coin nevertheless.
**FDC = Fleur De Coin = a very high grade MS++ or PR++ coin.