1917, 11¢ light green, perf 10 at bottom, showing transitional perforations from perf 11 to perf 10, Minneapolis, Minn. precancel, rich bright color, F.-V.F.; with 1987 P.F., 2004 & 2011 P.S.E. certificates. Scott No. 511a  $4,000. ONE OF TWO SOUND EXAMPLES OF THE THE 1917 11¢ ISSUE SHOWING THE TRANSITION FROM PERF 11 TO PERF 10. The Philatelic Foundation to date has certified only five examples of the 11¢ transitional perf variety. Of the five, three examples are faulty. $0 (Image)