I have this 1988 penny that has a half inch slight crack running parallel on outer edge. Is this worth keeping or are these type of errors rare. On the back behind AMERICA, you can see the line from crack from Obverse
Worth keeping? Yes, as these types of things (die cracks, cuds) add interest to otherwise mundane and abundant coins. They don't always add value, and as to rarity.........well, I've yet to find a die crack on an Lincoln/Zincoln. Welcome to the forum.
I explained to you what you have on your other thread. The indentation is not a crack, is caused by a worn die. Die Deterioration issue. It's common and not worth keeping.
True on the items you mentioned. But did you look at the Cent in question? It's none of those. Just Die Deterioration.
Looks too straight to me to be a die crack(it still could). I guess it could be a die scratch - is it raised?