The "space" (宇) designation on this issue refers to the Thousand Character Classic system used by the Joseon government to differentiate output from its numerous concurrent casting furnaces — each furnace received a unique character, making attribution possible even centuries later. The Board of Works, the Military Training Command, and several other agencies all operated independent mints simultaneously during this period, and without this character system the coins would be essentially indistinguishable by origin.
Brass coinage was mandated by royal decree in 1742 after chronic copper shortages forced a compositional shift from the earlier pure-copper issues.
The "space" (宇) designation on this issue refers to the Thousand Character Classic system used by the Joseon government to differentiate output from its numerous concurrent casting furnaces — each furnace received a unique character, making attribution possible even centuries later. The Board of Works, the Military Training Command, and several other agencies all operated independent mints simultaneously during this period, and without this character system the coins would be essentially indistinguishable by origin.
Brass coinage was mandated by royal decree in 1742 after chronic copper shortages forced a compositional shift from the earlier pure-copper issues.