Altimeter, Sensitive, 35,000 ft, Type KB 31/01
Here is an Sensitive Altimeter, made by Kelvin Bottomley & Baird aka KBB Instruments, under license from Kollsman, Type KB 31/01.
This sensitive altimeter displayed altitude using 3 pointers. The first and longest indicated 100's of feet, and the second indicated 1000's of feet. Ten-thousands of feet were indicated by a third and smallest pointer. The knob adjusts the altimeter to the barometric pressure as displayed in the small inset window.
It is experienced but in good condition given its age. The glass and case are intact. The knob rotates firmly. Measures 3.25 inches diameter and ~4 inches deep.