In a nutshell, what a COHERER is : The coherer was a primitive form of radio signal detector used in early radio receivers during the era of wireless telegraphy in the early 20th century. The device consists of a tube or capsule containing two electrodes spaced at short distances with metal filings dissolved in the intermediate space. When a radiofrequency signal is applied to the device, the metal particles stick together or "coexist", hence the name COHERER, reducing the high initial resistance of the device, thus allowing a much greater direct current to flow through it. In a receiver, the current would activate a doorbell or Morse card recorder to record the received signal. The metallic filings in the coherer remained conductive after the end of the signal (impulse) so the coherer had to be "decoherized" by beating it with a clapper operated by an electromagnet, every time a signal was received, thus returning the coherer to its original state. Coherers remained in widespread use until about 1907, when they were replaced by more sensitive electrolytic and crystal detectors.
This is a wonderful VERY RARE specimen made by Dr. physicist / scientist Adolf SLABY, an "electric" device from the early 1900s invented and created thanks to the contribution of German / Austrian military technology and research (period!). As shown in the pictures, this coherer was contained in that metal package, probably also from the same historical period, obviously the "loose cotton" that packs and protects it is nowadays since its original packaging has completely unraveled.
This COHERER is certainly an article by great COLLECTORS of the history of Radio and communications , of its origins, of the history of our Marconi, of the Count d'Arco (collaborator of Slaby), Tesla, Dr. Tuma, Lecarme, Popoff, Ducretet and other experimenters / scientists of the time; besides the importance of knowing the history of companies such as AEG, BRAUN, TELEFUNKEN, SIEMENS, technical laboratories of the MTC Navy, the Austrian-Hungarian Imperial Army (KuK), etc ..
The Coherer has been tested and is " work in order " compatibly with the possible performances for a component MORE THAN 110-115 YEARS from its realization!
The information on the importance of the discovery of COHESORE (COHERER) that can be found on the WEB is remarkable, even with clear references to the very rare coherer produced by SLABY.