Engine Temperature Indicator, 0-350deg C, Mk I, 6A/620 RAF Air Ministry
This is a fine specimen of a WWII-era British Engine (or Cylinder Head) Temperature Indicator, Mk I, type 6A/620, indicating up to 350deg C for each engine, as used in aircraft of the RAF, RCAF, and RAAF.
According to the guide Types and Location of Instruments in RAAF (Royal Australian Air Force) dated 1943, which cross references to those used in RAF aircraft, the 6A/620 was used in Beaufighter (using 2) and the patrol bomber seaplane Short Sunderland (using 4).
It is New Old Stock, and bears a serial number indicating a year of manufacture of 1943. The instrument is in it original bottom carton, the lid having lost its way over the years. Measures ~2.5 inches square and ~2 inches deep. An exceptional find, indeed.