Actually it is the hub for the screw unit. Sorry, I never realized that could make a difference.
I found what I am looking for on the site www.campyonly.com. In the timeline they made several brochures can be found and the Euclid brochure had the ball size specced!
Melvin, It's a very good site used it a lot myself lots of info on it.
Now spoil my evening and say It's a set of the Euclid Large Flange hubs you have got