Altimeter, Type C, Tyco, 25,000FT, WWI to 1926 Air Service USArmy
Here is an Altimeter used in military aircraft of the Air Service, US Army, which existed with that name from 1918-1926 until it was renamed Air Corps US Army. Crudely measured altitude from 0-25,000 ft, which was pretty high for aircraft of that era and requiring supplemental oxygen for the crew to exceed ~12,500 ft based upon modern standards. The knob would rotate the face of the dial while the pointer remains fixed to set the present field elevation. The knob turns, and there is still a metal government seal wired into place at 4 o'clock to provide evidence if opened. The glass has some dust on the inside. An example of aircraft in which this appeared is the Nieuport 28 fighter.