1977 black penny… Error?

[Anita]

I want to find the reason of this peculiar color.

[MintErrors]

Once coins leave the US MInt, it's very difficult to know exactly what happened to them. Color itself does not qualify as an error or variety. By the looks of the coin, it might be suffering from " environmental damage. The most common is the coin was simply dropped on the ground somewhere, and later picked up and placed back in to circulation. If the coin has residue in the recesses of the coin,and it looks pitted, it is probably environmental damage.

[Anita]

Good explanation, Thank you.

[MintErrors]

You are very welcome.