The CDV-720 is one of the early issue Civil Defense instruments. I haven't been able to find an exact issue date for the first CDV-720s. The first 720's were originally issued in the late 1950's with the CDV-710. The Victoreen Model-2 is the only CDV-720 that I know of that was manufactured with a plastic case. The early versions of the CDV-720 (Chatham and Victoreen Model-2) were declared obsolete and went through disposition like the entire family of CDV-710s. Many of the early CDV-720s that are found today have had the labels defaced and the "CD" logos marked over. This was done during the disposition process.

The CDV-720 is a high-range radiological survey meter that can discriminate between Beta and Gamma Radiation but only measures Gamma. The range of the CDV-720 is 0-500 Roentgens per hour. The sliding cover on the bottom of the meter case blocks Beta particles when closed allowing only Gamma radiation to pass through the detector. When the cover is opened this allows Beta particles to pass through the very thin metal membrane on the bottom of the CDV-720's Ion Chamber resulting in detection of beta radiation.