mint block of 18 (positions 1-6, 11-16, 21-26), second printing (86.B), overprint shifted down and at an angle resulting in positions 1-3 with "Canal" only, positions 11-12 and 21-22 with "Zone Canal" (86e), and the balance of stamps with overprint split vertically (86.5a), couple trivial perforation separations, very fine, an extraordinary block which is the largest multiple of the "Canal" only stamp and perfectly illustrates how these errors occurred, 1976 APEX certificate (Scott $7,400 as singles)