Wow! This is an amazing number of replies in one day. I won't be able to respond to everyone individually because of the volume, but I'll try to provide some more helpful information.
The first thing we did was request his entire military and medical record. No word yet whether they were lost in the fire, but they have our request and will get to it eventually. In the meantime we're trying to strengthen his case. We have good descriptions from him, but the best thing we can think of is getting him a buddy statement or finding a unit history that places him where he claims he was.
His claim is for PTSD, arising from an undocumented assignment to protect a water tower over night. He was there more than once, but we can't place him there on paper (although we don't have the full record yet, we know that it reflects his Korea service but not his traumatic nights at the water tower). He provided us with photos and personal letters from his time in service, but they only help us place him in Korea. None of the pictures or correspondence make mention of these water towers. There were apparently many of them, so someone else must have had similar orders (documented or undocumented).
Again, thank you SO MUCH for all of the helpful suggestions. I was not aware of the Korean War Project and will check that out now. I'm fairly familiar with the VA claims process, FOIA requests, etc., but I don't know a lot about the Korean conflict because most of our clients now are returning from service in the Middle East.