Matt, If you can get him to show you his discharge papers, that would be a good start. It would tell you what unit he was with. I believe the 1st Marine and 5th Marine Divisions served in The Korean War. You show be able to go to their association web sites and post a message in their guestbook. My father was there and to this day he will talk very little about it. He has nightmares and can still smell the death of the battlefield. They way these men where treated when they returned home, was uncalled for.