This would have been an accessory for the Very Rare NASA Nikon F3 "Large" camera which flew on many early Space Shuttle Mission. Nikon built this camera specifically for NASA space flight, and it was designed to accommodate this film magazine with a 250 frame capacity.
The film back has the NASA part number SED33101575-301 with serial number 1029, and includes original dark slide. I also have a NASA Nikon F3 "Small" camera for sale in a separate listing. Please refer to the pictures for details. The item "Vintage Space Shuttle NASA NIKON F3 Large Camera 250 Exposure Film Magazine Back" is in sale since Monday, December 4, 2017. This item is in the category "Cameras & Photo\Vintage Movie & Photography\Vintage Cameras\SLR Cameras".The seller is "itsanamazinglifeforsure" and is located in Denver, Colorado. This item can be shipped worldwide.