Jacob Auch (1765-1842), student of Philipp Matthäus Hahn and later mechanic at court in Weimar, built several adding machines around 1789/90. Three of those original machines have been preserved until today (Landesmuseum Württemberg in Stuttgart, Mathematisch-Physikalischer Salon Dresden, Museum Boerhaave in Leiden). Auch had probably already helped with the building of adding machines in his master’s workshop in Echterdingen. In 1787, he started up his own business as a clockmaker in Vaihingen an der Enz; and soon after he introduced his own adding machine. The crucial constructive element of the 8-digit machine is the so-called ten’s switching rail which guarantees a reliable tens carry. Additionally, it has a storage mechanism to save single-digit factors. The machine was intended for money calculations and therefore has a non-decimal carry over (60 kreutzer = 1 guilder) at the second place. For subtraction, the complementary digits applied in red writing have to be used. The Arithmeum has a replica in its collection that was manufactured according to the original from Stuttgart. Auch dedicated that one to Charles Frederick, Grand Duke of Baden. The 3D animation was made by Rebecca Munz and Philipp Ansorge as a work project, modeled after the original in the Museum Boerhaave in Leiden. The video serves as a vivid example of the functioning of the tens switching rail.