This is an extremely heavy duty calculator made of 3/8" thick plastic. It is approximately 2 1/2" wide and 12" long.
If the exposure rate is measured at a specified time, the slide rule can calculate the exposure rate at any other time. It will also calculate the dose to personnel for specified time intervals after a nuclear explosion. The two slides are reversible. One side of each slide has data pertaining to fallout generated by explosions over the sea, while the other side is used for calculations involving explosions over land.
Reference
B.W. Soole. The RADIAC slide rule for the computation of external radiation dose from nuclear fission products. Journal of Scientific Instruments Vol. 29 (June):