Mach Speed Indicator (Machmeter), Type A-2 Kollsman F-86

This is an exceptional example of the Type A-2 Machmeter as used in the Korean War-era US Air Force F-86 Sabrejet Fighter, indicating mach speed from .5-1.5 mach.  Made by Kollsman, part number 958BU-5-03.  

From the F-86A Flight Manual dated 1957:

A Machmeter is provided as primary flight instrument for indicating speed.  The Machmeter is extremely valuable, particularly at high altitudes, because its reading is more closely related to true airspeed than is indicated airspeed.  For example, at 45,000 feet, and indicated airspeed of 240 knots is actually a true airspeed of 510 knots.  This true airspeed is indicated on the Machmeter as Mach .89 at 45,000 feet or Mach .77 at sea level. Thus there is a difference of only about one-tenth Mach number between 45,000 feet and sea level, while indicated airspeed varies 270 knots. 

This Machmeter has a serial number prefilx of AF49, indicating a manufacturing year of 1949 for an order by the US Air Force.  It is in exceptional condition. Measures 3.25 inches diameter by ~7 inches deep.