Hiya peeps! I came by this thread late cuz someone just asked me something about Jin's headstone, and a search for a headstone screenshot brought me here. I've read a few pages of posts, but I don't have time to read all 29! Anyway, in case you don't have a translation of the headstone, here it is (I got my mom to translate it):
The date on the far right (9/22/2004) is the date of Jin's death.
The date to the immediate left of that (11/27/1974) is the date of Jin's birth.
The top two symbols of the main middle part is Nam Hae, which is apparently Jin's nickname & translates literally into "South Seas."
The rest of the main middle part means Jin Su Kwon's grave.
The left part lists Sun Hwa Baek as his wife and has her birthdate (3/20/1980).
As others have noted, Jin's death date on the headstone is the date of the crash. Given that it specifically lists the grave as Jin's, I don't think it's a double grave (as some have suggested). I'm guessing it was therefore erected after the Oceanic 6 got off the island. I'll leave the rest of the guessing to you all.
Thanks for the screenshot!