The purpose of this paper is to reveal the philological importance of the hand copied Maessi sangseo pyeong (梅氏尙書平) at Dankook University. It was in 1810 that Jeong Yag-yong (丁若鏞, 1762-1836) wrote this book when he was banished for 18 years to Gangjin, a small town in south-western coast of the Korean peninsula. Drawing on a wealth of annotations on the Classic of History (尙書), Jeong``s book insisted that the Old Text Classic of History (古文尙書) was forged by Mei Ze (梅색) in Eastern Jin. According to his epilogue of 1834, he revised this book twice after he was released from exile. He embraced opinions of scholars such as Shin Jak (申綽), Kim Mae-sun (金邁淳), and Hong Hyeon-ju (洪顯周) who dwelt near Jeong``s hometown and he found that the conclusion of Qing scholar Yan Ruo-qu``s Shang Shu Gu Wen Shu Zheng (尙書古文疏證) was very similar to his own. There have been several accounts that point to the differences among the hand copied versions and the published version of the book. But the original version had not been discovered, and thus, what Jeong had changed at that time is not clear. In this paper, I am able to clarify that the the Dankook University copy (vol. 1 3, odd volume) is the original version and UC Berkely copy (vol. 1 9) is the first revised version, based on a philological comparison between the two copies. While I have been writing this paper, vol. 4 9 of the original version had been exhibited at Seoul Art Center and National Museum of Korea. More philological research is needed in the future to illuminate the entire original version.