Altimeter, Sensitive, Type C-12, 50,000 ft, Air Corps US Army WWII B-17, B-24, P-38, P-51
Here is an early WWII-era Sensitive Altimeter, Air Corps US Army Type C-12, made by Kollsman. part number 671K-03. 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. It has a serial number stamped on its face with a prefix of AC-42, evidence of a manufacturing year 1942.
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 hidden behind the 1000's pointer. The knob is used to adjust the altimeter to the barometric pressure as displayed in the small window at the 3 o'clock position. See spec sheet in the photo gallery.
It is clearly experienced but in reasonable condition given its age. The glass and case are intact, and the knob rotates, changes the barometric display, and the pointers move. Measures 3.25 inches diameter and ~4 inches deep.