It's not aluminum. It's not an error. It's damage. It could be plated, or, the copper plating could be removed giving it a grayish color. If it is...
It looks like some foreign material (glue?) as it has discolored the top of the N.
It's just a hundred dollar bill. There's no fancy serial, it's not old or rare. OK it's in good condition. So what? Brand new bills come out every...
I've read that, but I've never heard anyone call them that.
Star note look up says run size 3.2M total 3.2M. And when I click your link it says run size 3.2, total 6.4.
I don't know what that black goo is. F/VF
You can't chase after something if you have set a boundary.
Separate names with a comma.