horizontal pair with right stamp the error, trace of original gum, fine, one pane of the 10c received the overprint at a slight angle resulting in this error, although there are traces of three letters at left they are well away from the design and this is the unique example of the error (another copy previously thought to exist was proven to be a forged overprint), one of the great rarities of Canal Zone philately, ex-Plass, signed H.F. Coleman and 1969 APEX and 1993 Philatelic Foundation certificates (Scott $3,000)