The Palace of Desdemona

The Palazzo Contarini-Fasan, aka the Palace of Desdemona, Venice
One of my favourite palaces on the Grand Canal is the diminutive Palazzo Contarini-Fasan, which dates back to the fifteenth century.

It is also often called the Palazzo di Desdemona, although what connection it has with the unfortunate wife of the insanely jealous Moor, no one seems to know. 

I was photographing the palace the other day when I noticed something curious about the stone tracery of one of the two balconies on the second floor. 
The wheel tracery of the balcony, Palazzo Contarini-Fasan, aka the Palace of Desdemona, Venice
The 'wheel' of the tracery at the right end is turning in a different direction to its three neighbours. It is actually turning in the same direction as the 'wheels' on the first floor. 

The palace now holds two mysteries for me.