Thanks for the responses. If it's any help I've also found out that Criss Angel performs this on one of his Mindfreek Series 2.
It appears that the magician 'borrows' two wedding rings from a couple of specs and after a few rubs in the right place, they are joined together. Now I don;t know if Angel uses stooges with gimmicked rings, but the DVD that I saw somewhere was, or appeared to be for this same effect and in the description it said if I remember correctly "two borroed rings".
I'll keeo looking but I spent this afternoon checking out all 89 pages of video's on the Alakazam site so that's one off the list to check out

(also built a great CUPS list at the same time

)
There's also a similar sounding routine on the Dave Jones DVD called Real World Magic
http://www.rsvpmagic.com/real_world.html if anyone has this title and would care to provide a brief description?
Member of the Magic Circle & The 2009 British Isles Close-Up Magician of the Year
It's not really an optical illusion - it just looks like one!