My guess is the ping-pong balls didn't have painted on numbers but had LCDs showing the numbers which could be sent to the balls electronically.
Any other thoughts ?...
1d (10 letters). Must have one's head in the clouds to be in one of these! ???S????R 19d (8 letters). It can be worked out...especially after a work-out ??P???T? 23d (6 letters). Going to be similar...
Which Michael Jackson song is your best song or songs? - Say Say Say - Give it to me - They dont care about us - Dirty Diana and the list goes on.............