1. This circular slide rule is for calculating the effects of a nuclear bomb blast.

2. It was very simple to use - well if you only had a 4 minute warning you would not want anything too complicated. By setting the weapon power and moving the cursor to the distance from the blast you could read the following:
-   Crater depth as a function of rock type.
-   Crater radius also as a function of rock type.
-   Degree of blockage from debris.
-   Static overpressure.
-   % killed.
-   % trapped.
-   % untrapped seriously injured.
-   type of damage (e.g. collapse of bridges, telephones out etc.)

3. On the back there was a table of fire situation showing the limit of isolated fires.

4. The naming is interesting: "nuclear weapon effects computer" using "effects" a completely neutral word not, for example,  "nuclear damage" or something more accurate.