unused Canal Zone, 1926, 5c Dark Blue type B overprint, 'CANAL' inverted (86b), in horizontal pair with normal (pos. 7 and 8 of the second printing), L. stamp the error, natural s.e. at T. as always (showing most of the guide line), fresh, full o.g., perfs. slightly in at R., nearly fine, rare, only 29 errors recorded, Scott retail $950.00+ photo