Found this relic while I was looking for something else.

The M1 Radiac calculator, which produces your expected radiation dose, given the reading from a Geiger counter or one of those, the elapsed time since the bang, and how long you’ll be exposed:

ABC-M1 Radiac Calculator

If you’re a belt-and-suspenders type, you might carry a dosimeter, too, which calls for a homebrew charger or, better, an official one.

The M4 Nuclear Yield Calculator which, according to those Official Instructions [Update: dead link], gives incorrect answers and has been replaced by the M4A1:

M4 Nuclear Yield Calculator

They’re basically circular nomographs, made from stacked plastic disks, with various index lines and notations. You could use the flat nomographs with a ruler, but what’s the fun in that?

All inside a vintage plastic pouch:

M28 Pouch

Some of the stuff around here, well, I hope I never have a need for…

[Update: That comment there has a link to a DIY version. Go for it!]