My continued research into Leica cameras that were used by NASA has yielded another interesting result. This Leica camera was used in conjunction with a spectrograph and was used on the Gemini V and VIII missions. Longer missions during the Gemini program gave astronauts more time for scientific experiments, often created and monitored by other government agencies or academic institutions. Scientists at the U.S. Weather Bureau (now NOAA) created this camera attachment so it could simultaneously record a spectrum and an infrared image to determine cloud heights.
The camera appears to be a model M3. It is unknown if any special modification were necessary for this specialized use.
For more info on the Leica-NASA connection got to:
LEICA M3 ON ENDEAVOUR SHUTTLE MISSION
NASA LEICA Ig
LUNAR LEICA – UPDATE WITH PICTURES
SURVIVAL OF THE FITTEST