I just bought the car...the old tensioner is an SKF from Germany...the TB has been changed at least once since there are white marks painted on the sprockets...
the new tensioner does not fit over the mounting stud...I would doubt they swapped out the stud to make an old style tensioner work...
Hmmm...I looked at your pictures and first off, the nut and washer is not the correct fastener for the tensioner stud....it should be a flange nut with a 13mm head... same as what holds your windshield wiper arm on.
Next, the threads on the stud looks a little dodgey to me....can you measure them to verify they are in fact metric threads? The fit of the incorrect washer screams metric, but let's be sure about the threads.
Reason I ask this is due to the white painted marks on the sprockets, just trying to ascertain the degree of tooef that has gone on here.
Look at where the threads begin on the stud and see if that puts you within clamping range on the correct (shiny, black roller) tensioner. Reason for this is that I've heard of a case where a VW gasser tensioner stud was used on a TDI which did not allow for adequate clamping force because you simply run out of threads. This was not factory mind you, but an egregious tooef.
Since the stud you have is larger in diameter to what should be there, either;
A: the original stud threads became boogered and was replaced by drilling and tapping out for larger stud, thereby requiring the incorrect tensioner, or
B: The individual responsible for this work received the wrong tensioner and replaced the stud with an oversize incorrect stud to make it all work.
Both of these are extremely likely since you mention in the other thread the presence of white painted marks on the sprockets. Once you see that, you know
prima facia the TB job was done stunningly
wrong.
