IM-113A/PDR GM Survey Meter (ca. 1960)
The IM-113A, manufactured by Nuclear-electronics Corporation, is a beta-gamma GM survey meter that reads up to 20 mR/hr. While it has no speaker, there is a covered jack provided for headphone use. In addition, there is a light next to the meter face that indicates the count rate- each pulse is indicated by a flash of the light. The only control is the range switch.
Unfortunately, I have not found any references describing the IM-113 and the tentative date for the IM-113A is based on a packet inside the case dated September 1960.
Range: 0-0.2, 0-2.0, 0-20 mR/hr
Size: 9” x 6" x 4.5"