This is a 1951 calculator / computer titled Radiation Dosage Calculator, For Fission Product Radiation, Copyright 1951.  It as manufactured by Consolidated Nucleonic Company.  It has three, 3, layers to calculate radiation dosage from 15 minutes to 50 years based on bomb size of 1 kiloton to 100 kilotons.  On the backside are directions on use.  A portion reads: All times are measured from the time of the atomic explosion……..   It measures 4.5 inches in diameter and made of celluloid plastic.  It is very bizarre and controversial, but is a piece of our American calculating history when folks were forced into a defensive mode like building underground bomb safes to school drills of hiding under a desk.  The potential of world wide nuclear war is still of concern, but this rarely found calculator is truly an amazing machine to predict the casualties.