Collecting Korean coins can be pretty confusing because not much is known about Korean coins.  Also, the history of Korean coins do not go as far as China or Japan.  Being occupied by Japan in early 1900s and of course, there is the Korean War.  Most of the Ebay items you will see are mostly from 1900s. Few are from late 1800s.  When I buy Korean coins, I look at many aspects of the coins before I even consider buying or bidding.  Here are some guidelines that I go by when I buy Korean coins.  Hopefully, it will be useful to you when you are buying Korean coins.

1.  Gold coins:  Highly recommend getting them if the price is right.  The Bank of Korea does not mint too many gold coins.  Last gold coins minted by The Bank of Korea was for the 2002 World Cup and before that, 1988 Seoul Olympics.  Question is - how much should I pay?  The gold coins minted on or after 1988 Olympics go for about $100 to $200 above the current bullion value.  For example, 1988 Seoul Olympic 1 oz gold coins goes for about $800 to $850 in PF 68 condition (remember, the gold price per ounce back in 1988 was less than $300).  The 2002 World Cup gold and silver coin set (two 0.5 ounce gold and two 1 ounce silver and two 0.5 ounce silver)  will sell about $2500 due to limited mintage.  However, the gold coins minted prior to 1980 command much higher price due to very limited mintage.  A gold coin from 1970 might fetch anywhere from $1500 to $3000 for 1/4 ounce coin.  If the gold coin is from late 1800 to early 1900, the price will jump to $500,000+ due to very few surviving species.   Bottom line - any Korean gold coins are worth to your collection.  The money pay for the Korean gold coins depend on your desire to own one and/or how deep your pocket is. 

2.  Other coins:  Any coins that were minted in late 1800s and early 1900s are worth collecting.  Coins with denominations of "chon", "yang", "fun",  "hwan", and "won" (before 1970) are worth collecting for they are harder to find.  Uncirculated condition is preferable but will command higher price.  Silver coins from early 1900s are highly desirable.  I recently saw early 1900 silver 20 yang graded MS62 by NGC sold for $315.  For regular strike coins, the coins from 1955 to 1969 will command higher price.  Highly recommend buying uncirculated coins because circulated coins will not be worth much.  The coins that were minted on 1970 or later are not worth much, therefore, I really do not bother with them. 

3. Commorative coins:  Highly desirable.  Silver commoratives minted on or before 1980 will command higher price than coins minted after 1980.  It is all got to do with Korean economy.  The mintage is low for commorative coins minted before 1980.  Expected to pay between $100 to $200 per coin if you are interested. 

4. North Korean Coins:  I really do not have much information about North Korean coins.  It is the collector's taste for North Korean coins. 

If you have any question, please feel free to email me.