George Walsh Gunsmoke credit Mistake

Phillip, he is not credited. He is uncredited by way of an "attribute". This is the way IMDb lists individuals that receive no "On Screen" credit. There is nothing wrong with the listing as it stands.
You yourself in your description above confirm his participation with this statement, "was archive footage at best and only on the title intro". So that makes the uncredited credit correct, and therefor no change is needed.
Please note that IMDb makes exceptions to it's rules based on a case by case scenario.
This surely would qualify as that because George Walsh held the same position on the long running "Radio Series" "Gunsmoke"
We can wait for IMDb staff to reply. Thanks for bringing this up. But I felt that a full description of the facts were in order here.
Cheers