:::: Thanks for the great outline.  I'm afraid that the image of a letter falls into a "primary source" category in my opinion.  If there's nothing else in those articles mentioning KA, you'll need to find another secondary source; I incorrectly assumed the newspaper articles covered both.  You can read about the distinctions at WP:OR.  Again, my opinion based on experience, but I'll do some searching and see what I can find in other cases.