According to a statement in the American Journal of Philately, of April, 1871, this issue was withdrawn from circulation between June 11th and September 30th, 1851. The instructions of the Department to the deputy postmasters, concerning the distribution of the next issue, published in June, 1851, order that these five and ten cent stamps must not be recognized as prepaying letters after the 30th of June, 1851, and request the public to return them to the deputy postmasters, in exchange for others of the new issue. The report of the Postmaster General for the year expiring June 30th, 1851, and published in the fall of that year, further states: "Directions for the destruction of the dies and plates, employed in the manufacture of the stamps formerly used, have been given, and for counting and burning such stamps as have not been issued to postmasters or have been returned." These facts probably explain the extreme rarity of unused stamps of this issue, and the re-engraving of the dies by the Government, when it was considered advisable to make an exhibit of all its issues of adhesive stamps at the Centennial Exhibition. The existence therefore, of a specimen of four unused five cent stamps, adhering by the sides, and another of four unused ten cent stamps, adhering also by the sides, in the private collection of Mr. Sterling, is worthy of notice. The latter specimen, at any rate, is probably unique, and though called whitish paper by him, has nevertheless, the bluish tint, and certainly is not _white_ paper. NOTE. There are _proofs_ however on white paper. XVIII. THE ISSUE OF 1851. The Act of the XXXI Congress, Session II, Chapter XX, approved March 3rd, 1851, and entitled: "An Act to reduce and modify the Rates of Postage in the United States, and for other purposes" reads: