Altimeter in Display Case, Aviation Section US Signal Corps, 15,000FT, WWI

This is an Altimeter used in military aircraft of the Aviation Section, US Signal Corps, which existed from 1914-1918 and was the WWI-era precursor to today's US Air Force. This altimeter crudely measured altitude from 0-15,000 ft.  By loosening the small retaining lever, gripping the knurled rim of the faceplate and turning, the numerical scale rotates clockwise or counter-clockwise while the pointer remains stationary, to correct the altitude reading as required.  See the altimeter depicted in the JN-4D Curtiss Jenny cockpit at the Yanks Museum. The altimeter is in exceptional condition given its age.  The altimeter measures 6 inches diameter and ~2.5 inches deep.  The wood-framed and glass display case measures 11 x 9 x 3 inches.