What does 'R' designate in Olympus MFT lens names?

Like the subject says can anyone please tell me what the 'R' in Olympus MFT lens names stands for?

E.g. What does the "M.Zuiko Digital 14-42mm f3.5-5.6II R" have, that the "M.Zuiko Digital 14-42mm f3.5-5.6 II Standard Wide Zoom" doesn't?

Looking at the descriptions these pages, it is not at all obvious, to me:

http://www.olympus.com.au/Products/PEN-Cameras/PEN-Lenses/M-Zuiko-Digital-14-42mm-f3-5-5-6II-R.aspx

http://www.olympus.com.au/Products/PEN-Cameras/PEN-Lenses/14-42mm-f3-5-5-6-II-Standard-Wide-Zoom- (PEN)-(1).aspx

At first I thought aha! retractable, then noticed the other was also retractable.

Then I noticed that one of the descriptions mentioned "the first version", so again aha! "revised", only to then notice that later version was the non 'R' version.

I also noticed that all the 'R' models were illustrated in silver metal finish,, but then again not all silver metal finish models are 'R' versions, so that is obviously not it.

So please what is 'R' inOlympus lens nomenclature?

Thanks in advance.