Altimeter, Tyco, 20,000FT, WWI to 1920's US Navy

Here is an Altimeter used in early military aircraft of the US Navy, very similar to the Type C altimeter used by the Army Air Service from WWI thru 1926.  Crudely measured altitude from 0-20,000 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 rotates the face of the dial while the pointer remains fixed to set the present field elevation.  

Measures ~4.75 inches diameter and ~1.75 inches deep. It is in terrific condition given its age.