Is this coloration just a chemical reaction? Is it desired ?
Cleaned. Not desired.
Your cent was harshly cleaned and is starting to retone. As @Mwallace said, these are not desirable. Use it fill a hole in your Cent album until something better comes along
How do you know it has been cleaned?
multiple, and I mean MULTIPLE small abrasions.
Your cent is severely damaged....Looks as if it were in a parking lot for months. It was found and cleaned of dirt and schmutz.... the cleaning residue is starting to tarnish. Good for an album until a better one comes along. Cheers, RickO
Your early date Lincoln has character.
Or, at least, when my dad had nothing nice to say, he'd state that.