This is the perfect “mini-probe” GM tube. It is sensitive to Alpha, Beta, Gamma, and X-Ray radiation. This tube was manufactured to very rigid mil specs during the Cold War specifically for the U.S. Navy.  Each tube has a unique hand-inscribed individual serial number indicating that it had been fully tested for quality and function before being released from the factory. 
   The tubes were used in highly specialized radiation measuring equipment for the Pacific Atomic tests. They are surprisingly sensitive when checking for Alpha surface contamination in areas where this dangerous form of radiation might have attached itself to any kind of food or water that could be taken internally.  These came to us directly from U.S. military surplus storage in Taiwan, where America had a military presence until 1979.
   The 6108 is constructed of stainless steel and ceramic. One end of the tube is covered with a thin layer of mica. This allows for the detection of Alpha radiation.