Altimeter, Sensitive, Type C-12, 50,000 ft, US Army Air Force WWII
Here is a WWII-era Sensitive Altimeter, Air Corps US Army Type C-12, made by Kollsman. The C-12 Altimeter was used across all aircraft of the Air Corps US Army, including heavy bombers B-17 and B-24, medium bombers, B-25 and B-26, Fighters P-38, P-39, P-40, P-47, and P-51, and transports C-46 and C-47, according to the Maintenance Interchangeability Chart dated Dec 1943.
The C-12 Sensitive Altimeter displayed altitude using 3 pointers. The first and longest indicated 100's of feet, the second indicated 1000's of feet, and the third and smallest indicated 10,000's of feet. The photos shows the first two pointers, and the smallest pointer is just peaking from behind the 1000's pointer. The knob is used to adjust the altimeter to the barometric pressure as would be displayed in the small window at the 3 o'clock position. See spec sheet in the photo gallery.
It is in good condition given its age. The barometric pressure scale does not appear in the small window at 3 o'clock, but may be able to be repaired. The glass and case are intact, and the knob rotates stiffly, and the pointers move. Measures 3.25 inches diameter and ~4 inches deep.