I reckon the 10c was stamped on later. MUCH later.
I also think it had hand painted edge spots which either wore off or someone tried to remove.
I've seen the same on other denoms.
I'm not certain it was a 10c chip when it was at the casino. Shouldn't the back say NO CASH VALUE?
OR
The casino did use them and painted the spots so they didn't get confused with the 25c chips in a stack.
I've always wondered why they had so many overstamped NCV on the back also. Did they change their usage? Or did Gaming tell them they didn't meet regulations and it was cheaper than re-ordering?