I bought a couple of old radiation kits off of ebay in order to show the difference in the readings between an uncalibrated one and one that has recently been checked. During the 1950’s, Civil Defense put out several types of radiation kits by the thousands.
The makeup of these kits depends on what they were used for. I purchased a shelter kit with two types of meters, several dosimeters, and a charger. Depending on how they were stored, these kits are either in perfect order and only need calibration, or inoperative like mine. Someone had stored my meter with a battery installed, and over the years the corrosion damaged the meter.
Like I said in the video, you cannot see, taste, smell, hear, or feel radiation. Without a meter you can easily receive a lethal dose if you happen to be in a strong field. I don’t personally worry about the rad/nuc aspect of prepping, because I am familiar with my states plan, my location, and my general ability to get a meter if needed. But preppers prepare for things they feel are worth prepping for, so if you choose to prep for a rad/nuc event, then make sure you research enough to buy a meter that measures what you are looking for and that it has been checked with the last 12-18 months to ensure it is reading accurately.
I only know of one laboratory that will do repair and Calibration of Radiological Instruments from the civil defense era. I have never actually purchased from them, and I do not receive any compensation for this from them. But if you own or want to buy a surplus CD radiological meter, you should visit KI4U at http://www.radmeters4u.com/calibrate.htm to see how calibration works.