Here is another nuclear disaster aid: the Radiac Calculator ABC-M1A1. This one is plastic and 4.5 inches in diameter.
This is not as nice looking a wheel as the other one, but that's a minor consideration during its use, I guess. For some reason, the outer disk has discolored while the inner one has not. Odd.
I found out something about both of the r
The RADIAC Calculator No. 1 was produced by Blundell Rules Limited of Luton England. Since it is based on the Radiation Dosage Calculator designed by William Orr in 1951, and since the company moved to Weymouth in 1956, it is safe to say that it probably dates from 1952-1956. It works as follows: if the exposure rate (roentgens/hr) is known at a given time after a nuclear explosion, the calculator predicts the exposure rate at any other time. It also estimates the dose to personnel who are in the area at specified periods of time after the explosion.
The ABC-M1A1 RADIAC Calculator is used by the US Army to determine the dose rates and doses to personnel after a nuclear explosion. It is the military version of the "Radiation Dosage Calculator" developed by William Orr.
There's a whole museum online of nuclear calculators and other relics of the atomic age.
Check it out. It's really interesting! You can read about both of these wheels there.