The producing companies used box end wrenches for checking size. They were 1/2 inch and 9/16 inch or 5/8 and 11/16 inch, etc. The wrenches hung on the marble machine at the start of the rolls. Done by vintage producer's, Jabo and current machine made marble makers. The company boxed sets used zeros has size indicators. I have never heard of any machine made marble company using 2/3 as a marble measurement. But could be possible ?