Clara Schumann’s cousin Wilhelm Wieck owned a company named Pianoforte- und Physharmonika-Fabrik in Dresden since 1861 which means that he not only produced pianos but reed organs or harmoniums as well. The instrument presented in the Robert Schumann House is a reed organ with pressure system from the 1860s — this type is much less common than reed organs with suction system. It has twelve stops with three rows of reeds for treble and bass enabling a different timbre; the five octaves are divided between e’ and f’.
You can listen to Robert Schumann’s chorale ‚Wenn mein Stündlein vorhanden ist‘ from 1856 (RSW app. R18) played by Thomas Synofzik on the Wilhelm Wieck harmonium.