Good Morning Wayne!
In my interview with John Campellone the owner of Our Bar I asked that very question. John said he worked at the Nevada Club (Diamond Jim's) during the time the rims of the 50 cent pieces were painted. According to John the rims were painted to designate various parking lots. Black for one lot; red for another.

I mentioned to John I never saw any 50 cent chips and or/dovetails painted anything but black. I also stated that with rims painted black and the chips in a rack with a real $100.00 chip on both ends it could give the impression of a complete rack of $100.00 when counted down in the cage and/or vault. He smiled and politely changed the subject! I think you get the message.<g> Best, Jim