Specifically Kyros is speaking of this piece -- the stop bracket that has an open hole in it:
GStopBracket.jpg

All Williams have a rubber grommet to let the nlylon hit it instead of the metal bracket. In the above case, PBResource supplied the fiber "hat" shaped links. I know some Gottlieb's used a square nylon link that directly impacts the metal, but in this case the fiber and the pivot would be impacting the metal at the hole.

I only know Bally/Williams so am of no assistance. Hopefully someone with Gottlieb knowledge can shed some light on this.