I have written about South Korean coins in narrative format in the past at my main coin page,
http://www.dokdo-research.com/koreancoins , but it seems that many people interested in these coins are looking for database-formatted information that online world-coin references like numista provide.
However, I find many errors in their databases with their Korean-coin listings. To be fair, they are trying to catalog a whole bunch of world coins so there's only so much that they can do. I want to make sure that I don't make similar mistakes, so I will update any of this information when I find errors or new data. I'll also update this database with more coins, i.e., commemoratives, if I get the chance.
Take a look if interested:
http://dokdo-research.com/southkoreancoindata.html