||The shafts on the backside have a 'Abstandsring 4mm' and a 'Achsadapter'. The Achsadapter of course doesn't have a real Rastkupplung, but it fits snugly on the outer end of a Rastachse. However, in order to make it last, I had to stick a little piece of plastic in to give it better hold.
The Achsadapter is small and flat, and functions as a lever that can be turned 90 degrees left or right.
In the picture you can see two rows shafts for two 7 segment displays, with a Zahnstange in the middle. The 2 displays are mirrored, so they can both be close to the Zahnstange. The Zahnstange is used to slide a motor up and down to move the levers.