Some time after the air mail stamps converted from definitive stamps which were put on sale in 1932, the regular air mail stamps of the 2nd & 3rd Peiping Print and those of the Hongkong Print were supplied to Sinking and sold without any overprint. In the beginning, the 2nd Peiping Print stamps were sold to match the converted air mail stamps. However, the wording〝限新省貼用〞(restricted for use in Sinkiang) was duly overprinted on such air mail stamps and the 〝Austerity Movement for Reconstruction〞stamps by same chops(wood and brass) after the Government had announced the exchange rate (5：1) between Legal Tender notes and Sinkiang local currency, effective from November 1, 1942. Overprinting was done in the following manner：(1)Wood Chop Red Character Overprint .At the commencement of the overprint only eight denominations of air mail stamps(15￠, 25￠, 30￠, 45￠, 60￠, and $1 of the 3rd Peiping Print and 25￠and 50￠of the Hongkong Print) were in stock in Sinkiang. Subsequently, the Directorate General of Posts sent seven additional denominations of air mail stamps of the same print to Sinkiang, thus making a total of fifteen denominations, which were overprinted lot by lot in red by a wood chop bearing big characters.(2) Wood Chop Black Character Overprint On May 25, 1944, a small wood chop was cut for overprinting air mail stamps in black ink. Only seven denominations of air mail stamps were then in stock, but with the subsequent arrival of four additional denominations the total came to eleven denominations in all. They were overprinted in lots and placed on sale.(3)Brass Chop Black Character Overprint. In September of the same year, the Sinkiang Postal District Head Office was instructed to use brass chops in lieu of wood ones, wherefore a brass chop in Li style characters was used. The 25￠stamp of the 3rd Peiping Print, which had arrived in Sinkiang by that time, was the only enomination of air mail stamps overprinted by hand with the brass chop in black. As the Sinkiang Postal District stopped the use of all kinds of stamps of the Peiping and Hongkong Prints from the end of March in that year in accordance with instructions from the Directorate General of Posts, the sale of air mail stamps verprinted in black was limited to philatelic requirements.