On December 1, 1962, the Ministry of the Posts and Telecommunication issued a set of commemorative stamps-----C92 "Scientists of Ancient China (I) , the values in set was 8. They introduced several scientists of ancient China, namely, Tsai Lun of East Han Dynasty (the inventor of paper-making process), Sun Si-miao of Tang Dynasty (Physician) , Shen Kuo of Song Dynasty (Geologist), Guo Shou-jing of Yuan Dynasty (Astronomer). In the stamps, there were the dates of birth and death and dynasties the scientists lived in under each name. Tsai Lun was a famouse scientist in East Han Dynasty. He invented the paper-making process. Since the date of his birth is unknown so in the stamp it should read "Tsai Lun ( ? ------121 ) , Han Dynasty ", but the stamp designer wrote in the painting of the stamp " Tsai Lun ( BC ? ------121), Han Dynasty" . The error hadn't been discovered until it was about to be printed out. The printing workers then had to take out the word " BC" one by one from the dies. Through an oversight, one was not picked out; therefore, the error remained in the No. 16 stamp in every post office sheet. During the sale, some stamp collectors found out the error by chance. The Stamp Issuing Department took the errors back. But several thousand such stamps were not returned so they are very valuable.

On Novemer 21, 1997, on the auction during the " '97 second Coins and Stamps Expo, one C92 error of Tsai Lun, new triple-pairs, was sold at 61,000 RMB.