In the second picture of the Kassel wheel (Secunda Figura/Die andere Figur) there appear to be some strange markings in the top center of the drawing. As usual, unusual writings has their reasons.
Here we see a close-up of the symbols. The first is a special "o", the next is some kind od doodel, though drawn with a very high accuracy.
Again, we have documented their purpose, as they are placed there to confirm the existence and appearance of the Orffyrean Code.