 These were the current Postage Due stamps of the United States, consisting of the denominations of one, two and ten cents overprinted with the words "canal zone" in one 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.