No argument from me on the connection between the first two LA Dodger and SF Giant pennants below. Same distinctive "A" and "S" used in both city scripts. Same construction. Therefore, Greg, I agree: they were likely made by the same maker.
But,
if that maker was WGN, then that does not answer why these two pennants look nothing like others we're
100% certain were by WGN from that year. And that, to me, is where the comparison falls apart....
Here's two 1958-dated LA Dodger and SF Giant pennants we know for certain to be by WGN. And another from later that year for the Milwaukee Braves. As you can see, these last three are
nothing like the first two. So, that's why I think their maker may be someone else.
Good discussion!