Air Navigation Computer CPU-26A/P, Dead Reckoning

Here is an Air Navigation Computer as used by US Air Force navigators from 1940-~1980 for dead reckoning navigation.  This one appears to be from the 1950's.  

There is a small screw missing, but a replacement screw can certainly be found locally.  Measures ~4 inches wide and ~7.5 inches long in its case.