I watched "The Legion of Old Timers" episode of "The Lone Ranger" the other night. The guy that played "Bob Kittridge" looked vaguely familar. I waited fer the credits. Low and behold, it was DeForest Kelley;. Dr. Leonard "Bones" McCoy for "Star Trek" fame.
That episode aired on October 6, 1949. BTW, that was his first TV appearance. He was in 7 movies before that.
Slim