RCL Model 10303 (?) GM Tubes  (mid 1950s)


These two beta-gamma GM tubes were manufactured by Radiation Counter Laboratories of Skokie Illinois. Unfortunately, I have no hard information about them. They appear to be very similar to what became the RCL Model 10303. The latter, like these tubes, was painted black, had a three pronged base, employed a silver cathode, and was approximately 4 3/4" long and 5/8" in diameter.

The numbers that appear on the base underneath the letters RCL, 7-55 and 7-56, almost certainly refer to the dates of production


Size:  7-55  4 3/4" long,  5/8" diameter

Wall: glass,  estimated thickness 30 mg/cm2

Cathode: Inner surface of glass wall coated with silver 

Operating voltage:  estimated 900 volts



Radiation Counter Laboratories catalog, Radiation Detectors, no date. Estimated late 50s



Donated by Ron Kathren

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Last updated: 07/25/07
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