So there is no general consensus that these were ever intended to be billiards balls. The theory I proscribe to is they were intended to be used by a newspaper to drop inside 50 gallon drums of news print ink and used to thin the ink out when placed on a vibration stand just like those marbles inside a can of spray paint
The variable sizes coupled with random colors lends credence to this theory over some of the others.
That is a very interesting theory, Mr B.