They are Brass Core chips. Very heavy cores with plastic injected.
I think there might have been 4 original colors. Seller is showing 3.
They were sold in the HR Cafe gift shop.
Not used in the HR casino.
They are not RARE, they are in a lot of chip sellers and collectors books but the prices have been fairly consistant at $40-$60 each.
Many have been altered, color changed, flamed, etc.
Here is one that was altered.