Here are 2 of a few threads on the subject https://www.cointalk.com/threads/1959-jefferson-nickel-improperly-annealed-black-beauty.250868/ https://www.cointalk.com/threads/19...auty-just-how-many-are-still-out-there.90771/ Yes. They have a small premium. I have 2 NGC certified. But just because a nickel is dark colored does not make it improperly annealed. Most are environmental damage.
@willis243 Use capital letters in your thread title. It will make more sense to new and younger collectors. Such as 59 Jefferson Nickel Black Beauty
Here is my 1959 and 1964. It could happen on any other clad coin and year. Only if it's an actual improperly annealed error.