text: Similar to the CD V-715, the CD V-720 is a fixed-position ionization chamber survey meter. Unlike any other survey meter, however, this unit has a movable beta shield on the bottom of the unit for detecting high levels of beta radiation. When slid to the open position, beta particles are allowed to directly penetrate the ionization chamber. With the beta shield closed, only gamma rays can penetrate both the shield and ionization chamber. This meter reads from 1 R/h to 500 R/h (×1, ×10 and ×100 scales). The CD V-720 was produced in 4 models (1, 2, 3, and 3A), Chatham made the model 1, Landeds Fray and Clark made the model 3 (along with Victoreen Instruments), and Victoreen Instruments made all other models. All but the Victoreen model 3 and model 3A used a combination of D and 22.5 volt B batteries, while the Victoreen models 3 and 3A just used 2 D batteries. By 1962 113,231 had been procured, but in September 1985 FEMA declared all models except the Victoreen model 3 and model 3A obsolete.