In these pictures you see how the carriage can be shifted from the left to the right. When the outer two machines are given the same input, it is possible to make combinations of x and y for coordinate transformations, which is necessary if the grid that is used is not oriented the same.
All the levers for switching the machine work as follows:
The top lever marked 2 1/2 1 engages the revolution counters that are indicated, i.e. the left one, both or the right one only.
The lever between the two machines on the left operates the rotation direction of the revolution counters - identical or opposite. On a positive turn of the crank, when the counters are set opposite, the left revolution counter will switch to red numbers.
The bottom lever between the two right machines switches between identical and opposite rotation of the two rightmost machines. When set to zero, only both outer machines rotate. The outer two machines always rotate in the same direction.
The silver +/- indicators have no function other than to serve as a memento for the user what exactly he is doing, and to keep track of the signs of the input, multiplicator and results in the various registers.
The two final levers to switch between . and .. have the same function on the triple machine as the do on the single machines - determine whether the input register is cleared together with the result register.
This is the bottom of the machine with the type plate and serial number
All things considered, the price I paid was decent. I had to buy another double Brunsviga to get the correct lever for clearing the carriage, and some comma sliders, and the machine needed a really good cleaning (and it is still a little spotty - I suspect it may really have been in a moist basement rather than on an attic ...), but now it works as intended, so if anyone has a need for coordinate transformations, feel free to ask!