We used to have a club member in the Golden Gate cage. Very helpful to chippers. Several years ago, she brought out a box of unused green chips and would sell at face if you wanted them. This was probably 6-8 years ago and am pretty sure all are gone, but that's where the UNC ones you see for sale from time to time likely came from.

It never hurts to ask about unused chips at the cage. That's how I was able to get unused Wynn $20 poker-room chips a couple of weeks ago. Still have one extra if someone needs it. I do have a $10 tip invested in the dozen mixed chips I got that day, though [g].