Nuclear Instrument and Chemical Corp Model 2584 (Early 1950s)
The Model 2584 is a portable ion chamber for gamma measurements. It was manufactured by the Nuclear Instrument & Chemical Corporation of Chicago, Illinois.
According to an advertisement from 1951, the Model 2584 "is a MODERN development of the wide-range, low level AN/PDR-T1 Meter."
Like the AN/PDR-T1, its most distinctive feature is the fact the fact that the display changed color as the range switch was rotated. The range switch is coupled via a connecting rod (rather than with a chain as with the T1) to the mechanism under the meter face that changed the display. Each range was indicated in a unique color.
As seen to the right, pink (for danger) was used on the highest scale. I don't know why they used an M rather than a K to indicate 1000.
Detector: Ion chamber
Ranges: 0-5, 0-50, 0-500, 0-5,000 and 0-50,000 mR/hr
Dimensions: 10” x 6” x 5”
Batteries: Based on the schematic, I am guessing that it might have used one 1.3 volt, one 1.5 volt, two 2.6 volt, one 22 volt, one 45 volt and three 60 volt
Nucleonics, June 1951, back cover.