http://wttool.com/Merchant2/graphics/00000001/normal/19900015.jpg
It's a 6 inch table.

The motorized ones I have seen essentially have replaced the handlwheel with a servo mounting plate and flexible coupler, I have exactly the same unit and am thinking of doing the same. mine is a Yuasa.
Al

Division master (UK based) supply kits to fit stepper motors to these rotary tables to go with there electronic controller.

Website is http://www.divisionmaster.com/

here's a site of some nice pictures and info on just what you are asking about....
http://www15.brinkster.com/candgresearch/