The mintmark was hit by another coin or something hard enough to make that mark. It's damaged so spend it.
I'm not seeing anything unusual.
MD but the O is a die chip. Not sure about the L but probably not what you want it to be.
Did you switch from Cents to Nickels? This one is damaged as stated.
DDD
I'm not seeing anything.
Some signatures add value and others lower the value as the note is considered damaged.
You are so correct.
X2
And that raised the question, how can this be the same coin? It must be two different coins, the obverse of a copper and the reverse of a zinc.
Separate names with a comma.