Serial numbers are not ancient history. In the last few years I have encountered normal, plastic house chips in Cyprus and Zambia, all with unique serial numbers. I think they were made by BG. It was fun to play 21 all night and check the number on every chip that passes through my hands, sometimes finding interesting numbers. At times the number of digits can roughly indicate how many of each denomination were manufactured, such as four digits would prove no more than 9,999 pieces.