Cylinder Head Temperature Indicator, Type B-9, US Army Air Corps WWII

This is a WWII-era Type B-9 Cylinder Head Temperature Indicator as used in aircraft of the US Army Air Corps before and during WWII.  The indicator measures the temperature of the cylinder head via thermocouple from a single engine, from 0-350 deg C. Made by Weston, part number 102316, with a serial number prefix of AC-42, evidence of a manufacturing year of 1942. The type number and AC US ARMY are imprinted on its face.

According to the US Army Air Force Maintenance Interchangeability Cross Reference Chart dated Dec 1943, this indicator was used in fighter P-47 Thunderbolt (see photo of P-47 instrument panel from its flight manual dated 1945), light bombers A-20 Havoc, A-25 Shrike, A-28/29 Hudson, A-35 Vengeance, and A-36 Apache, and trainers AT-6 Texan, AT-17 Bobcat, BT-12 Sophomore, BT-13 Valiant, and BT-14 Yale. See spec sheet in photo gallery.

Measures 3.25 inches diameter and ~ 2 inches deep.  It is in decent condition for it age. The glass and markings are clear and case are intact.  The remnants of green and red paint markings on the glass to indicate operating limits of the last model aircraft in which this was installed. The max operating limit of the P-47 was 260 deg C, about where the red mark is on this instrument.  Was this from a P-47?  We will never know...