Radio Altimeter Altitude Limit Selector Switch, SA-1/ARN-1 for AN/APN-1 P-63 which stands for Air Forces

which stands for Air Forces US Army(difficult to see in photos)

or Machmeter

clearly made for an Air Corps order

It was also used in versions of US Army Air Force WWII fighters P-38

It was fitted with a louvered shutter and shot panoramic

Radio Altimeter Altitude Limit Selector Switch, SA-1/ARN-1 for AN/APN-1 P-63 which stands for Air ForcesThe WWII era Radio Altimeter Altitude Limit Selector Switch, SA 1 ARN 1 was a component of Radio Set AN APN 1, used to measure and indicate to the pilot the altitude over the terrain during flight. See image of spec sheet. The Radio Altimeter was used in a number of aircraft of the US Navy where close monitoring of height over terrain was critical, such as torpedo bomber TBM Avenger (see image from TBM Flight Manual), dive bomber SB2C Helldiver,