2-Mun Coin of the Yi Dynasty 1742-1752 Copper diam 28 mm, wt 4.78 g The legend on the obverse, Sang Pyong tong bo, includes the name of the organization which first issued these coins in 1633. The Sang Pyong Stabilization Bureau attempted the creation of a stable monetary system. The legend means ‘coins of the Stabilization Bureau', and also, in a literal translation, ‘always exact coin', that is, hard currency of a stable value. Subsequently, a large number of mints – as many as forty – continued to make these coins over the next 250 years.