Altimeter, 20,000 ft, US Gauge AW-2 3/4-32-L

This is a fine example of a WWII-era Altimeter, similar in specs to the B-12 only with a center knob instead of left corner, made by US Gauge. Similar to those used in the C-43 Beech Staggerwing, see page from its pilot manual dated 1944.

This is a standard, or non-sensitive, altimeter in that it has one pointer (sensitive altimeters have 2-3 pointers). This altimeter measures to 20,000 ft of altitude, with the pointer rotating once from 0-10,000 ft., and then again for 10-20,000 ft. It does not have a barometric scale, but the center knob is provided with which to rotate the dial, so that the pointer may be set to zero at any existing atmospheric pressure between 28 and 30 inches of mercury. 

It is in exceptional condition given its age.  The knob, while stiff, still rotates the dial. The glass and case are intact.  Measures 3.25 inches diameter and ~3 inches deep.