These were released by Correos of Nicaragua in 1995. All eight teams of the KBO in '95 make up this stamp set with 9 stamps per team (8 players, 1 mascot). For each team, players make up the outside border and the mascot is in the middle. The players name is in full Korean as well as the family name and first two initials in English. At the time of this post I have forgotten to scan the back. I will include one later. On the bottom of the sheet it says in Korean, Korea Pro Baseball (한국프로야구). The photos are of games played in Korea, during the season I'd assume.
I may consider breaking up a team set to get a player graded by PSA (maybe Jong-Beom Lee, Min-Tae Chung or Ki-Tae Kim). I have a Mattingly Grenada stamp graded so hopefully they will grade these as well. I will even see if I can add this to TCDB but I have a feeling it's not allowed since these are stamps. I added the checklist for this stamp set to TCDB located here. It is listed under Oddball (as is the Grenada), not Korean League.