80 Years of Postal Service Miniature Sheet [Constant Variety (Pane F)] Unused, Sen Denomination ★ There is a mark on the upper right corner of the 2-sen stamp (upper right) that looks like the letter "F" rotated 90 degrees (constant variety). It is called "Pane F." ★ Price reduced considering the condition. Glue loss, aging, etc. present (see images).