Hi Peter,
Thanks for your email. I also thought there is no restriction, since I don;t see any retaining rings or such. Looking at it under a loupe I couldn't find any seams either. But from the construction I am sure it is retained with a ring somehow.
Do you think the retaining ring could be bonded? Any idea what kind of adhesive they might have use?
Will try tapping it gently and if not work will try it with boiling water towards the end of the week.
Thanks again for your advise.