line, diagonal fashion along the bottom area of the stamps. The regular issue of U.S. Postage Due stamps were overprinted again in 1925, with a variation in the overprint, with CANAL over the word ZONE. Postmasters in the Canal Zone received strict orders not to sell any of these stamps to the public in unused condition. These orders were apparently followed as none of the unused Postage Due stamps had surfaced. In April, 1915, these stamps were replaced by a set of Postage Dues supplied by the Panama Government, and those remaining in the Post Offices were called in and destroyed. The new stamps had a pleasing appearance, consisting of three values: one, two, and ten centesimos de balboa; Printed by the American Bank Note Company all three of these stamps were of the same color, olive brown. Final years The final years of the Canal Zone saw few stamps issued—those that were issued were mainly for new first-class postal rates (the first-class rates paralleled those of the United States) The last stamp (fifteen cents) of the Zone was issued on October 25, 1978, and depicted one of the towing locomotives and a ship in a lock. Thereafter Panama took over the administration of postal service and, after a brief transition period, Canal Zone stamps became invalid. 1975 reprints In 1975 three stamps originally issued in 1928—1929, and one issued in 1946, were reprinted on the rotary press as coil stamps. 4-cent Thatcher Ferry Bridge A 4-cent Thatcher Ferry Bridge commemorative stamp (Scott 157) was issued on Columbus Day, October 12, 1962, commemorating the opening of the new bridge over the Panama Canal at Balboa. (See below image, left) Famous error One pane of fifty stamps was released without the silver ink used to depict the Bridge. This error is likely to have made this issue the most famous Canal Zone stamp. Three additional sheets of this error were discovered in the Philatelic Agency at Balboa, which attempted to print an additional 100,000 copies in an effort to reduce its value to collectors. The sheet was unknowingly sold in a group of 5,000 to a Boston stamp dealer, H.E. Harris, who successfully sued in federal court to stop the additional printing. Today, examples of this famous error are still owned by collectors and are valued at many thousands of dollars. The National Postal Museum is in possession of two of