Going through some rolls, I found this interesting nickel pictured. Does anyone have any idea how it got the copper overtones on it? And does it have value? Also, I run across slightly off center strikes in my nickel roll hunting. I mean, it may just be missing the rim on one side. Are they worth keeping? I've gone through several rolls of new 2020 quarters. Most have several nicks in them. Looks like the mint is pushing the coins out fast to catch up to the coin shortage. I put away a few that are nearly without a nick, but none are perfect.
Nickels are made of Cupro-Nickel Planchets. They contain 75% Copper and 25% Nickel. When exposed to a harsh environment the Copper tones. Not a mint error. Only worth 5 Cents. Same goes for Clad coins that look darker. Cupro-Nickel also.
Welcome to CT. It's a spender and it toned due to the environment it was exposed to. Not a Mint error.
Here are examples of dark Clad and Nickels I have found in dirt, soil and sand when Metal Detecting..