I recieved a 20 dollar bill 1991 from my sister a few days ago, Nothing seems wrong with it, its got a little bit larger quantity of planchetes on one side then normal, yet on the other side there is a massive smear that you can only see using a black light. Its on the left side, its not visible to the unaided eye either. odd... The Serial Numberis "AYC5583595" and the sigs are Knight-Dodge . I have no idea what caused this. It is definately not visible without a black light. It looks like the planchete ink exploded all over.