Jim, my thoughts on the caps are they were more of an aesthetic thing so the silver tips of the screws would not be seen through the grille opening.
That could very well be, although "red blood tipped exposed screws threads" are not aesthetic either.
The originals were black bakelite material, not soft rubber like the repro's.
I would still like to get some documentation on this. A TSB perhaps?
I had ordered a second set and was going to put one on that ground screw just to clean it up a bit. I was curious if they actually put a cover on that screw originally or not.
I took another look, you can't see that screw tip, by the battery, from the front. There is little to "adjust", "tighten", or otherwise access on that side, so no.
Jim