In 1883, Gustav Heyde and Karl Otto Büttner applied for a patent on a four-species switching latch machine that was however not manufactured in series production. Only four specimens of this machine are known in total, one of them is in the Arithmeum. The switching mechanism is slightly similar to that of Dietzschold’s and Weiss’ machines, which have both been presented as Exhibit of the Week already. The sequence of movements in this calculating machine is unusual and fascinating. It shows the extraordinary inventive genius of Heyde and even more of Büttner. The 3D animated video was made by Baris Gündogdu and Burak Celebi as a joint bachelor’s thesis following their attendance of the lecture about the history of mechanical calculating by Professor Dr. Ina Prinz. The attention to detail is outstanding in this video and makes the complex sequence of movements in the machine easily understandable. Enjoy watching!