Among the stamps with overprints reading 〝限新省貼用〞(restricted for use in Sinkiang), those bearing the characters 〝航空〞(air mail) were overprinted locally in Sinkiang in 1932, while other stamps were invariably overprinted by the Directorate General of Posts and issued to Sinkiang for sale. But during the years 1936-1942 only definitive stamps were overprinted as usual. All special issues such as the New Life Movement stamps, Austerity Movement for the Reconstruction Stamps, stamps in commemoration of the 40th anniversary of the Postal Service, the U.S.A. Sesquicentennial, and the 30th anniversary of the Founding of the Republic of China and air mail stamps of Peiping and Hongkong Prints, etc., were placed on sale in Sinkiang without any overprint.
On November 1, 1942 the exchange rate between the Legal Tender notes and Sinkiang currency notes was fixed by a government order at 5 to 1, necessitating overprint of a portion of the Austerity Movement for Reconstruction stamps for use in Sinkiang. Wood and brass chops were used for the overprint resulting in the following differences：
(1) Wood Chop Red Character Overprint. This was made in only five denominations in different quantities and souvenir sheets. The stamps were overprinted with a wood chop piece by piece. The characters of the chop were of the Regular-Writing style somewhat larger in size than the characters in another chop subsequently used. Such overprinted stamps are commonly known as〝Stamps of Red Big Characters.〞
(2) Wood Chop Black Character Overprint. A new chop was used on May 25, 1944, while the old one was destroyed. The characters on the new chop were of smaller size, and the overprinted stamps are thus known as 〝Stamps of Small Black Characters by Wood Chop.〞 When the chop was first put into use, stamps of 8￠28￠, and 33￠denominations were all out of stock, and only three denominations of stamps and souvenir sheets were overprinted. However, as the Sinkiang District had received instructions to stop the use of stamps of Peiping and Hongkong Prints, Austerity Movement for Reconstruction stamps thus oveprinted in black characters were sold for philatelic purpose only.
(3) Brass Chop Black Character Overprint. Not long after the use of the small character chop, the Sinkiang Postal District received new instructions to carve a brass chop for overprinting purpose. The brass chop was first used in September 1944 when a number of stamps in the 8￠and 33￠denominations were received in Sinkiang from the Directorate General of Posts. These were overprinted in black both by brass chop and by the small character wood chop. The characters in both chops were nearly the same in size, but those of the brass chop were of the〝Li〞style and easily distinguishable.