Precision Model 107C "Professional" (ca. mid 1950s)

The Precision Radiation Instruments Model 107, also known as the “Professional,” was a Geiger Mueller survey instrument designed for uranium prospecting and/or civil defense.

There is no speaker to provide an audible signal but there is a covered jack on the top of the instrument for headphones. The count rate could also be estimated by observing the small flashing neon light to the left of the meter face. A locked adjustment on the top of the unit permitted the surveyor to adjust the calibration – a source was provided so that the calibration could be performed in the field. The Model 107C was probably first appeared in 1954 or 1955 - reference dates for the Model 107 and 107B were 1950 and 1954 respectively.

Precision Model 107C "Professional" (ca. mid 1950s)
Precision Model 107C "Professional" (ca. mid 1950s)

Quoting a newspaper advertisement from 1955: "Professional Geiger Counter. First with the Percent Meter. $149.50. Easy terms. Yes! Its the same make and model (PRI-107C) used recently by two Ohio housewives to discover a multi-million dollar uranium deposit northwest of Buffalo."

Detector: GM tube (30 mg/cm2), connected to the meter with a non-detachable cable

Range: 0-0.2, 0-2 and 0-20 mR/h.


  • Model 107B—two 1.5 volt, two 45 volt and one 22.5 volt batteries
  • Model 107C—two 1.5 volt (RCA VS036, Eveready D99), one 45 volt (RCA VS055, Eveready 455) and one 67.5 volt (RCA VS016, Eveready 467) batteries

Dimensions: 3.75” x 4.5” x 7.5”

Weight: 6 pounds

Price: Model 107B: $139.50 in 1954.


  • Advertisement, Nucleonics May 1952, p 82.
  • Atomic Energy Commission Radiation Instrument Catalog No. 2, Part 2, page date April 17, 1950 (Model 107).
  • Atomic Energy Commission Radiation Measuring Instruments RIB (Part 2) Supplement, page SGM-49C, July 1, 1954 (Model 107B).
  • Advertisement for Dey Brothers in the October 27, 1955 issue of the Syracuse Herald Journal.
  • Precision Radiation Instruments. Model 106B "Lucky Strike" and Model 107B "Professional" Operation and Maintenance Manual. No date for Manual but the schematics are dated 1954.
  • Precision Radiation Instruments. Model 107C "Professional." Operation and Maintenance Manual. Copyright date 1955.
  • Jim Hill, personal communication.