Due to the urgent need in Taiwan, the Ah Chow (Asia) Printing Press, Hongkong was asked to overprint the characters〝限臺灣貼用〞(restricted for use in Taiwan) on a part of each of the four denominations of unit postage stamps then being printed. As the printing and packing of the registration fee and registration express fee unit stamps were all completed, they agreed to make only the overprint on the domestic letter and air mail unit stamps, the latter being grouped as under the category of air mail stamps. The other two denominations were, after their arrival in Taiwan, handed to the C.E.P.W., Taipei for overprinting. There is some difference between these two overprints. In the Hongkong overprint the characters are longer and larger, while in the Taipei overprint the characters are square and smaller in size. Both overprints were in black.