IM-53/PDR-8A and 8C GM Survey Meters (ca. early 1950s)

As the label indicates, this is an "IM-53/PDR-8A RADIACMETER," "a unit of the RADIAC Set AN/PDR-8A." It was manufactured for the U.S. Navy, probably in the early 1950s, by the Radio Corporation of America. It is described in Volume IV of Radiological Defense, which dates from 1950-1952, but as best as I can determine it is not referenced in the RADIAC literature of the1960s. As such, I am guessing that the PDR-8 was declared obsolete sometime prior to 1960. It was probably replaced by the AN/PDR-27 series. Both the AN/PDR-8 and the AN/PDR-27 used the same end window GM probe, had comparable ranges (up to ca. 0.5R/hr), and had displays that changed when the range was changed.

IM/PDR-8(A&C) GM Survey Meters
IM/PDR-8(A&C) GM Survey Meters

The range switch was connected via a chain pulley to a mechanism beneath the meter that changed the visible display. Only the range actually being employed (e.g., 0-10 roentgen per 24 hours) is seen! In addition, the different scales are given different colors! This greatly reduced the possibility of an incorrect reading.

IM/PDR-8(A&C) GM Survey Meters


IM/PDR-8(A&C) GM Survey Meters

The probe (see above) employs an end window GM window of which is 0.44 square inches and 3-4 mg/cm2 thick. The survey meter comes with a 36" telescoping "Probe Extension Handle" that can be attached to the probe. The AN/PDR-8A (above photo) is missing the extension, but the latter can be seen in the photo of the AN/PDR-8C. The headphones and check source are missing from both units.

The compartment in the carrying case that is used to store the meter is so tight that taking the meter in and out of the case eventually destroys the label (see above).

Quoting the Instruction Book for the AN/PDR-8C and AN/PDR-8D: "Radiac Sets AN/PDR-8C and AN/PDR-8D are portable, battery operated units, designed to detect and measure beta and/or gamma radiations... Their prime purpose is to detect and measure the amount of beta and gamma radiation to which personnel is exposed."

There are two controls. One is the Range Switch. The other has the following four positions: OFF, A, B, and READ. Settings A and B are used to check batteries A and B—there is no check for the C battery. When this switch is at "A" and the Range Switch set on the highest scale, the needle will be to the right of the "A" marking on the meter display if the battery is okay. The same procedure is used to check battery B.

IM/PDR-8(A&C) GM Survey Meters


Size: Kidney shaped, ca. 10" long, 6 1/2" wide and 7" high

Weight: ca. 11.5 pounds


  • AN/PDR-8A: 0-0.1(green), 0-1, and 0-10 (red) R/24 hrs
  • AN/PDR-8C: 0-0.5 (dark green), 0-5 (light green), 0-50 (green, yellow, red), 0-500 (red) mR/hr
  • AN/PDR-8D: 0-0.01 (dark green), 0-0.1(light green), 0-1, and 0-10 (red) R/24 hrs

Audio: Headphones, no speaker

Batteries: Two 1.5 volt (A batteries), one 15 volt (C batteries), two 67.5 volt (B batteries) 

Manufacturers and estimated date of first manufacture:

  • AN/PDR-8: Hoffman, late 1940s
  • AN/PDR-8A: R.C.A., late 1940s
  • AN/PDR-8B: Hoffman, late 1940s
  • AN/PDR-8C: Admiral ca. 1950
  • AN/PDR-8D: Admiral ca. 1950

AN/PDR-8A donated by Allen Brodsky.


  • Campbell, D.C., Radiological Defense, Vol. IV Armed Forces Special Weapons Project, Foreword dated January 1950.
  • Admiral Corporation. Instruction Book for Radiac Sets AN/PDR-8C and AN/PDR-8D. NAVSHIPS 91295. March 15, 1950.