Non clutched alternator pulley?

My car is a 1999 non PD tdi.  When I got it the tensioner damper was knackered, and doing nothing apart from making a noise.  I replaced the damper with a new one from ebay (the tensioner itself seemed fine).  About 8k later, this damper is leaking badly and the belt is flapping about quite a bit. 

Reading on here, this seems a common problem, caused by a knackered one way pulley on the alternator.  No problem I thought, I'll just replace the alt pulley and damper.  However looking at my alt pulley, it seems to be a normal fixed single piece one, without the bulky centre that's in the clutched version.  Mine is like this, found from the part number on the back of the alt.  

Were any cars fitted with a fixed pulley?  Or is this a bodge by someone who's had a worn out one way pulley and has replaced it with a fixed?  The alt looks like it's been changed relatively recently. 

Does anyone know if I can just fit the right pulley to this alt or do I need a whole new unit?  Don't want to be changing dampers every 6 months!