Altimeter, Sensitive, AN-5761-1, 35,000 ft, US Navy WWII TBM Avenger
Here is an early WWII-era Sensitive Altimeter, US Navy AN-5761-1 (former Army Type C-14A), made by Pioneer. part number 1583-2Q-A. This type of 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 Feb 1945. This one was made specifically for aircraft of the US Navy, including any USN versions of the above such as the PB4Y Patrol Bomber, SBD Dive Bomber, PBY Catalina seaplane, but also used specifically in the TBM Avenger Torpedo Bomber according to its Erection and Maintenance Manual dated 1945. It was likely used in USN fighters such as the F4F Wildcat, but this has not been confirmed.
The Sensitive Altimeter displayed altitude using 3 pointers. The first and longest indicated 100's of feet, the second indicated 1000's of feet, along the outer scale, and the third and smallest indicated 10,000's of feet. on the inner scale. The knob is used to adjust the altimeter to the barometric pressure as displayed in the small window at the 6 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. The knob rotates, but does not engage the barometric pressure adjustment mechanism consistently. This specimen has a service label from Naval Air Station Norfolk (VA) dated 1955. Measures 3.25 inches diameter and ~4 inches deep.