For what it's worth, I wouldn't put too much stock in the texture of screen printed graphics. That "fine grid-like pattern" you reference is the mesh imprint from the stencil carrier. Every maker used these. Some are more pronounced on the final product because, depending on the detail of the design being reproduced, the screen printer would use screens with different mesh counts. This one just looks like they used a coarse screen with a low mesh count.
I printed my "LA Dodgers v. SF Giants "1st. GAME" Pennant (1958)" (
https://pennantfactory.weebly.com/bl...e-pennant-1958) using a screen with a mesh count of 160. Anything less than this and the detail of the bridge wouldn't have come out. But for simple designs, like large, block letters with no detail--a lower mesh count will suffice, e.g., 110. Lower mesh counts permit more ink to pass through the screen, resulting in brighter, more opaque graphics.
There's
many variables when screen printing a pennant: mesh count of screen used; substrate used (wool, wool blend, or Duvetyne); ink used (lead or non-lead). Within each manufacturer, I'd expect to see evidence of these variables from one design to the next. Therefore, I don't really think each maker had a consistent "screen printing signature" you can use for ID'ing one company from the next. With pennants, that works for things like hand writing, letter scripts, and original artwork used on a piece; but, not so much for screen printing.
With one exception: secondary color applications. The way that each maker added colors to their white underbase during the manufacturing process
did differ. Some used really dull inks (Trench, ADFLAG); others used fluorescent Day-Glo inks (WGN, HANCO).