Bally had star insert that "plugged" the star base.
After the game is clear coated, the assembler would tap out the
plug from the bottom of the playfield. the sad part about this process at the time was
that it tore the clearcoat from the top of the plastic star base insert.

Note: Bally drop target rubber rings are always doubled.
The doubling helps the ball from getting stuck in between
each drop target space. Starting with the third incarnation
of Eight Ball Deluxe the company started to add thin metal
"L" shaped brackets to fill the void.
P.S. The game is looking good! Fantastic job.

My concern is the coil stops that are plated??? is the
brass current limiting rings that are at the base of each
coil stop bracket plated over? of so you may have trouble
with each solenoid being energized. Magnetism, magnetism,
magnetism.

Brass 28%
Zinc 27%
Conductivity, you might be O.K. Just concerned.
The plated stuff looks awesome.