Classification Of Korean Coins

There is a large article to be found on Korean mun coinage:-

Search Google:
'Korean Mun - Wikipedia'

So basically, Joseon Dynasty Korea began minting Sangpyeong Tongbo (the "Mun" cash coins) in the late 1670s. This was the nation's first successful currency and the longest lasting of any hard currency here. When the country created this currency, they used government-run and local mints and furnaces to create the coins. There were nearly 50 of these mints across the peninsula at every major city, province, and military installation. So they aren't public organizations, but are different mints across the country. To indicate a "mint mark" like we have today, the top character on the back of the cash coin was the hanja character of the mint. For example if the coin was made in Pyeongan, they would use the character Pyeong. Also, the mints began minting coins at different times as the cash coins began circulating throughout the country. So you will typically find that mints closer to Seoul have earlier dates than mints further away. For example the Treasury Department began minting 2 Mun coins in 1679 while the mint in Jeonla-do (southwestern Korea) began making that 2 Mun in 1742. The date also differs depending on the face value. While Treasure Dept 2 Muns start from 1679, 1 Mun coins from the same mint weren't made until 1731.

So while it may seem a little weird, it is a system that worked and the different mints and dates make for fun collecting.

Also, I absolutely hate western resources on Korean cash coins. For example the dates are wrong. The Seoul Charity Office didn't mint 2 Muns in 1695. They minted them there from 1742~1752.