Intercept Officers Equipment Kit, Type I (Navigation Computer) 1943 Martin was the US's first air

was the US's first air defense system (extensive history can be found here)

with an interesting history

or patrol observer

It has a service stamp SMAMA (USAF Sacramento Air Materiel Area at McClellan AFB

measuring vertical speed in a climb or descent from - 5 meters/second to + 5 meters/second

Intercept Officers Equipment Kit, Type I (Navigation Computer) 1943 Martin was the US's first airThis is a WWII era navigation computer in a kit "Intercept Officers Equipment Type I. This example includes two 2 piece USAAF Ground Speed Timer Calculators (for map scales 1: 250,000 and 1: 500,000) and 2 USAAF Rulers. The bottom of the metal case contains a mechanical computer to solve the wind problem. It has a locking mechanism and a movable arm for drift, adjusted for air speed, interconnected to the heading tracker. The lid contains tables and a