Altimeter, French Armée de l'Air, 0-4,000 meters Aera Type M40
This French altimeter, indicating altitude to 4,000 meters, is presumed to be WW II era from an aircraft of the Armée de l'Air. Made by Aera of Paris, Type M 40, it has a knob to adjust for barometric pressure, which is displayed in the window above center.
Measures ~3.25 inches diameter and ~2.75 inches deep. In reasonable condition given its apparent age. The knob turns and rotates the barometric scale.