The arithmomètre for Pope Pius IX is a special showpiece by Thomas de Colmar. During the fine-tuning of his machine design in the 1850s, he had produced such showpieces in various forms in order to present them as gifts to the potentates of his time and thus advertise his skills to the public.


The specimen shown here was ceremoniously added to the Arithmeum's collection in 2022 to mark the opening of the exhibition “200 Years of Arithmomètres by Thomas de Colmar”. With its dedication to a pope it is unique among mechanical calculating machines according to current knowledge.

The ten-digit machine for Pius IX bears the number 154 and, like the later series machines, rests in a wooden casket, albeit in its finest version. An intricate pattern of Boulle marquetry in brass and tortoiseshell lends the wooden case a radiant elegance.

Although at first glance the mechanical construction is almost identical to that of the series machines, there are still some striking differences in the details of the design. In his student research project, Kai Becher prepared the machine didactically and modeled and animated it with great attention to detail. Join us and discover the special features of this unique pearl among the Arithmomètres Thomas.