vertical pair with black handstamped overprint, used on January 18, 1955 cover to Madison, Wisconsin franked with 30c Rose lake and 6c Light brown pair (C12, C22), very fine and rare, from 1938 the Canal Zone Postal Service kept a stock of United States special delivery stamps, in 1954 the CZPS temporarily discontinued sale of US special delivery stamps at the advice of auditors so the Ancon postmaster produced provisional special delivery stamps from pairs of 10c stamps