Looks like a vise job. The letters are backwards in the first photo. lol That's a great looking error. Wish it were mine.
New millennium starts at year 1 since there was no year 0 and the old century and old millennium end on year zero. The error is cool. Will a slab protect it from zinc decomposition?
I think the letters/design on brockage coins are supposed to be backwards, since they come from another already struck coin. For vise coins, the underlying coin design are still there, due to comparatively lighter pressure applied. Just my thoughts.
100% definitely not a vise job. 100% genuine. The reverse side of this coin would have been corrupted if it were a vise job. Also, at least part of or all of the rims would have been flattened. Understand that an already struck cent failed to exit the chamber and was then struck into this coin, which is what constitutes a brockage.
You missed the lol. I think it's a great error. I just couldn't resist commenting on the backwards lettering as we see so many vice jobs that people consider errors. As I also said, I wish it were mine.