Some BK2K prototypes also had "Diamond Plating".
EXTREMELY RARE, as during the production run this was removed for cost savings and was replaced with a full mylar coating overlay.
Worst mistake Williams ever did with this game, beyond switching to an alternate plastics set, and changing the font color of the backglass.
NOS playfields for this game remain "unoptanium" and I have only seen 5 complete sets (upper and lower PFs) in over 20 years.