I recently purchased a BJ coin center chip from the late 70's. On one side there are 3 small, 1/16in. diameter, circles incused(?) into the chip. They are equally spaced and appear to be part of the manufacturing process but I have never noticed this before. Can someone please let me know if this is normal or if the chip is damaged? Other than the circles, the chip is in near mint condition. THANKS in advance to anyone who might help.