I see a dividing plate I could have but the divisions seem to the most unlikely to be of any practical use.
It has holes 61, 67, 71, 77, 81, 87, 91, 97 / 63, 69, 73, 79, 83, 89, 93, 99. OK, I can see this would be useful to divide a circle by 3,7, 9, 11,13 but then there is a gap in the odd numbers taking on again at 21,23,27,29,31,33.
So what use are these things? Am I missing a part of the picture? Maybe there is some procedure to use some holes from one circle combined with holes in another?