You can't see the internal rubber bushing (the "tensioning element") from the outside. The "rubber rings" you see on the front and rear faces of the tensioner are the ball bearing seals, not the internal rubber tensioning element.

The key is to watch if the pointer backs down the ramp as you relieve tension. On an old tensioner, it probably will not. In this case remove the tensioner and observe the orientation of the flats relative to the pulley axis. If not oriented as stated and confirmed in this thread: http://www.peachparts.com/shopforum/showthread.php?t=129793 the tensioner is not serviceable and must be replaced.

If you attempt to reuse it, you may end up bending the tensioner rod, and even if it does appear to tension the belt, after a few miles of driving you'll hear the belt screech due to lack of tension.

You'll be doing the job again!

Duke