IM-125E/PDR-43 GM Survey Meter (ca. 1960s)

IM-125E/PDR-43 GM Survey Meter

The instrument shown here is an IM-125E/PDR-43 survey meter that was produced by EON Corporation in Brooklyn New York. Nicholas Anton, founder of Anton Electronic Laboratories, founded EON Corporation in 1961.

The NAVSHIPS 94200.5 Directory of Radiac Equipment (ca. 1960) states: "Radiac Set AN/PDR-43 (XN-1) is used to measure gamma radiation and to detect beta radiation. The radiation sensing element is located in the forward end of the radiac-meter." The contract for the AN/PDR-43 (XN-1) was given to Electronic Products Co. of Mount Vernon New York in 1955. This particular example of PDR-43 is of later manufacture and probably dates from the 1960s.

The AN/PDR-43, like most Radiac instruments, uses a method for changing the meter display that only a few commercial instruments employ. When the range switch is turned, the range seen on the meter face also changes so that it is much harder (but not impossible) to misread the instrument. The PDR-43 has three selectable color-coded scales: 0-5 (pink), 0-50 (magenta), and 0-500 (purple) R/hr. The problem I have with it is that the difference in the three colors is not as apparent as you might like, and the numbers are extremely small. Old geezers like me need a large print version. I have other complaints: the handle is uncomfortable, the switches are too small, and their edges are too sharp. One nice feature: the meter face can be illuminated with a light activated by a small button on the top of the case.

IM-125E/PDR-43 GM Survey Meter

Detector: Miniature halogen quenched GM tube with mica end window.

Range: 0-5 (pink), 0-50 (magenta), and 0-500 (purple) R/hr

Size: ca. 4 1/4” x 7 3/4” x 3 1/2” (excluding handle)

Weight: 4 1/2 pounds

Batteries: Two 1 1/2 volt D batteries

Manufacturers: Electronic Products, Electro Neutronics, EON, Spectron 

Estimated First Date of Production:

  • AD/PDR-43 (XN-1) 1955
  • AD/PDR-43 late 1950s
  • AD/PDR-43A early 1960s
  • AD/PDR-43B early 1960s
  • AD/PDR-43C early 1960s
  • AD/PDR-43D early 1960s
  • AD/PDR-43E early 1970s
  • AD/PDR-43F late 1970s, early 1980s


  • Campbell, D.C., Radiological Defense, Vol. IV. Armed Forces Special Weapons Project, Foreword dated January 1950.
  • Naval Electronic Systems Command List of Radiacs in the Navy Program P-9670-1, February 1975.
  • Directory of Radiac Equipment NAVSHIPS 94200.5, no date, ca. 1961-62.
  • Defense Atomic Support Agency, List of Military and Civil Defense Radiac Devices. DASA 1243 revised, 1966.
  • Defense Nuclear Agency List of Military and Civil Defense Radiac Devices HQDNA (AR) 3M Revised, August 1987.