Electronic Products Company Model 5979 End Window GMs (1950s, 1960s)
These Model 5979 end window GMs were manufactured by Electronic Products Company of Mount Vernon New York for the United States Navy. In their outward appearance, they seem identical to the Model EP-70M which is described in the 1950 AEC Radiation Instrument Catalog. The Navy designation for the latter was BS-1 and the upper of the two tubes in the photo is stamped JAN-CY-5979/BS-1. These tube models were used in the military's AN/PDR-27 survey meters.
If these are indeed the same as the EP-70M, they are organic quenched tubes with a recommended operating voltage of 700 volts and a window thickness of 3-4 mg/cm².
The lower of the two in the photo has a red anchor stamped on the base (not visible in photo) and USN-CY stamped on the metal wall. It also has a removable metal cap to protect the mica window.
Size: 5 1/2” long and 7/8” diameter
Window: Mica coated with aquadag
Cathode: Stainless steel
Base: Single prong, brass (painted black), connected to cathode via glass insulator (painted black)
Atomic Energy Commission Radiation Instrument Catalog, Date July 1, 1950, page BG-1A29A.