Mach Speed Indicator (Machmeter), Mk 3A, Ref 6A/3300, RAF
This is a fine example of a Cold War-era Mach Speed Indicator Mk 3A Ref 6A/3300, as used in aircraft of the British Royal Air Force. The indicator displays aircraft mach speed from 0.7 to 1.3 mach. The serial number indicates a year of manufacture of 1958. The indicator is also marked with K.M.A.0201K, likely a part number. The RAF Air Ministry arrow emblem is marked on the rear case.
The adjustment screw at 6 o'clock position moves a white indexing bracket along the perimeter (shown between 0.95 and 1.05 mach in the photos), likely to indicate the maximum acceptable range for a specific aircraft.
The face of this indicator is similar if not identical to the mach indicator seen on the instrument panels of the Avro Vulcan strategic bomber and the Hawker Hunter jet fighter (see photos).
The indicator is in exceptional condition given its age. Measures 3.25 inches diameter and ~4 inches deep.