If you have noticed, the old design is a trial. This new
one seems to be hidden under the old design.
Seems that SBST is trialing the different design but hiding it
under the original one. Clever design... 
Its not hidden, the bells have indeed been replaced.
The additional yellow layer behind the original bells is just a
spacer so that the bell fits into the thinner poles of the
citaro.
And if anyone are wondering, the citaro poles are thinner than
those used on kubs, this is why the spacer is needed for installing
the bells.
