With a bent corner this note no longer would get an UNC status...Since it is small you could probably fix the corner fold and do a dry press and you will get AU 55... perhaps 58 if you get it out pretty well.
For the polymer series it get a bit more difficult because the clear area scratches up very easy esp. going through bank machines...I personally will tolerate one or two small hair line scratches but if I am to call it UNC the clear poly usually has to be crystal clear.