The hole in the top would be for checking phasing and a larger rectangular hole in the side would be for checking rotor tip to cap terminal clearance but iirc we were much better on that one after adding the NAPA Echlin MO 3000 rotor. Actually the holes can & should stay if the cap is in good shape as it lets out ionized air molecules that can promote crossfire sorta like the electrified air between outspread tree branches and the ground when lightning strikes the top of the tree but with phasing and terminal clearance corrected we are in much less danger of that happenening though it does go against the grain to eyeball a cap with holes cut in it & to not wanna change it. I'm kinda surprised that it wanted 25 deg of initial & I'm interested to see how that goes