Well Keith, I sit corrected!

I took a look at the specs and it does say zero alright. Well, I suppose it's virtually unmeasurable.
The old Mectrol site says;
"Accuracy. All bearings are precision class 6 bearings. The cam follower bolt circles are held concentric to 0.0002". This gives positional accuracies down to seconds of arc."

Now that would be nice!