Before the summer of 1949 all stamps required in Taiwan invariably came from the Postal Supply Department, Shanghai. After the fall of Shanghai this source was cut off, and all the stamps needed had to be printed locally. Due to the change of currency in Taiwan, the printing of definitive stamps had to be done quickly. As an emergency measure, three denominations of Dr. Sun Yat-sen Issue( $1,000 and$3,000 denominations of the First Farm Products Issue, with the value altered, and $5,000 denomination of the Second Farm Products Issue) bearing old Taiwan currency values were converted into postage-due stamps with the characters〝欠資〞(postage due) chopped at the top. At first the stamps were overprinted with four wood chops in a block. As the block wore out easily, it was replaced by a steel chop and the stamps were overprinted piece by piece. However, the sale of such stamps was suspended in 1950 when new postage-due stamps were issued.