Under the threat of nuclear war in the 1950s and 60s, Americans prepared for what life might be like if they survived an attack. The dosimeter is a pen-size scientific instrument with an eyepiece you look into at the top of the dosimeter and a charging contact at the bottom. It measures the amount of radiation absorbed by the device since the last time it was reset to zero.The dosimeter is reset by charging it with electricity using with a dosimeter charger, like this one. This device fills the inner chamber of the dosimeter tube with a high voltage charge. By looking through the eyepiece while this is being done, the user can manipulate the charger knob to reset the hairline indicator on the radiation scale inside the dosimeter to the '0' point. This sets the dosimeter to zero and readies it for use.