Airspeed Indicator, Maximum Allowable, Type F-5 w/Mach Limiter
This is a Cold War-era Airspeed Indicator, 0-700 MPH, Maximum Allowable, Type F-5, made by Kollsman and used in aircraft of the US Air Force such as versions of the fighters F-82 Twin Mustang, F-86 Sabrejet, F-80 Shooting Star, F-84 Thunderjet, F-89 Scorpion, F-94 Starfire, and trainer T-33. Made by Kollsman, part number 865FU-8-042, with a serial number prefix of AF-51, indicative of a year of manufacture for an aircraft order for the USAF.
The white main pointer rotates clockwise as the airspeed increases. The mach number limit is displayed at MPH by the red pointer and by the mach number in the inset window at the inside 3 o'clock position.The mach number limit is adjusted for the specific aircraft model by removing the blue hex screw cap on the rear case to reveal the limit screw, which when turned rotates the red pointer and the corresponding mach number. This is set prior to installation for the particular aircraft. When in flight and the airspeed of the aircraft reaches the striped pointer, the aircraft is at its maximum allowable airspeed or maximum allowable mach speed, whichever is less.
This instrument is in exceptional condition for its age. The case, glass and dial are in exceptional condition for its age. Measures 3.25 inches diameter and ~5 inches deep.