The Geiger-Müller counter is nowadays best known for its characteristic clicking noise and its function in radiation protection. But its genesis is – for several reasons – fairly unclear. It was developed by Walter Müller under the supervision of his former thesis adviser Hans Geiger in Kiel in spring 1928. The new so-called “Elektronenzählrohr” surpassed its predecessors because of its ability to detect less intense ϒ-radiation and cosmic rays. In the early 1930s the instrument that was soon baptized Geiger-Müller Counter quickly became canonical in the field of radioactivity and early cosmic ray research. It achieved this status despite the fact that the knowledge about its working, its construction and its handling was not transferred to a broader audience. Because of inter alia a highly restrictive secrecy policy by Geiger and Müller, only a few textual sources exist. As a result, the historical research field is difficult to grasp. However, an analysis with the replication method seemed possible. During the research I found an artifact of an early counter tube in the Smithsonian Institution. Walter Müller himself donated it in the 1970s together with five related notebooks. But the artifact’s analysis provided more questions than clarifications on the construction process. My paper will develop the genesis of the counter based on the three methods: the analysis of the available textural sources, the construction of the replica and the analysis of the process, and the reading of the artifact of an early counter as well as its historical classification. In doing so, I will discuss the evolution of the device as well as some aspects of the skills that are required in making and operating this device.