G'day,
examples in solid gold past 2003 are fitted with ceramic ball bearings for the rotor; that´s one of several changes to the GP3XXX range over the years. As far as i know, the rivetted/friction-fit parts are still being used; but then, it´s a well tried and tested way and not visible at all.
The ref. 25800 of course is a piece of continuing production, therefore the latest pieces always come with all that was improved meanwhile. Authorized GP dealers should be aware of the production date and may adress the specific details of the piece in question.
Hope this helps a bit?
Greetings from Germany,
Peter