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Yield Calculator which, according to those Official Instructions [Update: dead link], gives incorrect answers and has been replaced by the M4A1: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