EICO Model 803 Geiger Counter (ca. 1950s)
This particular Geiger counter was manufactured by EICO (Electronic Instrument Company) of Brooklyn, New York, a company whose primary business was manufacturing electronic test equipment, amplifiers, etc. Nevertheless, they obviously couldn't resist getting into the nuclear business. My guess is that it was a money losing venture, and if EICO produced any radiation detectors other than the Model 803 shown here, I am unaware of it. It almost certainly dates from the 1950s.
This is an inexpensive instrument aimed at the amateur prospector, someone who wanted to become rich but didn't want to spent a lot of money to do so.
There is no meter to display the data. The radiation levels were indicated via the headphones and a small flashing light (not seen in the photo) on the top front of the case. The only control is an on/off switch. The cover for the case simply snaps on—there are no screws to deal with. The GM tube, located inside the case at the bottom, was manufactured by the Nucleonic Corporation of America (NCA).
Detector: GM tube
Size: 2” x 7” x 4”