For sale here is a $1 Federal Reserve Note from Series 1969B (Kansas City district) that has a foldover error in the upper right corner. The fold does not have any of the design printed on it but there is a line  on the front side (which is normally trimmed off), which is used to align the cutting operation. Thus, the fold appeared to have occurred after the front was printed. The note is in high grade with a minor bend in the middle and light handling elsewhere, so probably XF or AU condition. Foldover errors like this are very unique and are sometimes called butterfly folds. This one is in high grade and on an older series of $1 bills and it is for sale here without reserve.