There are a lot of these around and should be re-calibrated for accurate readings.
An example of the CDV-715 survey meter.
By far the most common US civil defense meter on the market today. This is a simple ion chamber radiological survey meter, specifically designed for high-radiation fields for which Geiger counters will give incorrect readings (see above). Survey meters do not read alpha or beta radiation. They work by radiation penetrating the case of the unit and the enclosed ionization chamber to produce a visible reading between 0.1R/hr and 500R/hr (X0.1, X1, X10, and X100 scales).
CD V-715 Survey Meter
The CD V-715 was the most widely produced of all the Civil Defense radiation instruments with a total of 567,457 instruments produced. As far as I know Lionel, Victoreen and Landers Frary & Clark were the only manufacturers of the CD V-715. Here are 5 examples of CD V-715s. From left to right at bottom of photo, Lionel Model 1, Lionel Model 1A,Landers Frary and Clark Model 1A. The top row in the photo, Victoreen CD V-715 Model 1A and Victoreen Model 1B. Yeah, I know, they all look pretty much exactly the same.
The CD V-715 is a very high-range gamma radiation detecting instrument. It's not a Geiger counter.
To see the detecting range difference between the CD V-715 and the CD V-700 click here.
CD V-715 is a high range gamma survey meter for general postattack operational use. The ranges of this instrument are 0-0.5, 0-5, 0-50 and 0-500 roentgens/hour.
When properly calibrated, the response of this instrument is within the range of plus or minus 20 percent of the true gamma radiation dose from a Cobalt 60 or Cesium 137 radioactive source.
This instrument was designed for use by radiological monitors for the major part of their operation in the period following an attack. The instrument is primarily for surface monitoring survey but it can serve as supplemental equipment for aerial measurements. (continued below following photo)
Pictured above are a Landers Frary & Clark Model 1A and Victoreen Model 1B. The CD V-715 consists of a ion chamber detecting element, power supply, electronic circuitry to amplify the minute current from the detector, and a indicating meter. The detecting element of the the CD V-715 is an ionization chamber. (Click Photo To See Larger)
The CD V-710 medium range 0-50 r/hr gamma survey meter, which is similar to the CD V-715 except for it's range, and the CD V-720 high range beta-gamma survey meter have been replaced by the CD V-715. The CD V-710 will be phased out and replaced with the CD V-715 as states develop their own maintenance and calibration programs."
(From Radiological Defense Planning & Operations Guide SM-11.23.2 Revised March 1967 )
Military Manuals VICTOREEN CD V-715 Instruction and Maintenance Manual 2015-01-28
RADIOLOGICAL SURVEY METER OCD ltem No. CD V-715