A form of currency Eun Byeong (silver vase), shaped like the Korean peninsula, was issued in 1101 (the sixth year in the reign of King Sukjong of Goryeo). After Eun Byeong lost its value as a currency as the silver vase with high copper content was circulated, So Eun Byeong (small silver vase) was produced and circulated in 1331 (the first year in the reign of King Chunghye of Goryeo). So Eun Byeong was smaller than Eun Byeong but had higher purity, which increased its exchange value by 50%. One So Eun Byeong was worth 15 rolls of cloth. However, So Eun Byeong was no longer being used since it went from almost pure to having lower silver content over time. The circulation of So Eun Byeong was entirely prohibited in 1408 (the eighth year in the reign of King Taejong of Joseon).