Arirang Numismatics https://arirangnumismatics.wordpress.com/ The link above will take you to a new research effort on Korea's early struck coinage. This is the best history of these coins that I have yet encountered. He uses sources that haven't been used in earlier efforts to describe this period of Korean numismatic history. Absolutely incredible work. WELL worth a visit, even for those not familiar with Korean coinage. BTW: He's not done yet! He is continuing to write more articles as time goes on. Keep checking back for more content...
mlov43 - thanks for the link. Very interesting reading. There is an article issued by Journal of East Asian numismatics a while back about early Korean coins and German involvement. This was written by a researcher in Germany if I recall correctly. Interesting to see from a different perspective! https://issuu.com/jeandigitala1/docs/the_eleventh_issue_of_jean