EXTREMELY FINE (EF or XF): A very attractive note, with light handling. May have a maximum of three light folds or one strong crease. Paper is clean and bright with original sheen. Corners may show only the slightest evidence of rounding. There may also be the slightest sign of wear where a fold meets the edge.
Example - EXTREMELY FINE - Note the fairly sharp vertical crease at center along with minor handling creases at the upper right.