It’s a SIAC 486, uses an industrial backplane and a signal board computer. The military had tons of them for diagnostics on vehicles, use in test shops and anywhere you needed a portable computer before the Panasonic “tough book” or Getac or any number of other companies started selling rugged laptops. Everyone I have seen had a 486/25 or 33, 32 Megs of RAM and they used a removable IDE hard drive. The hard drive caddy has an electric heater to keep the drive warm. The power supply is a 24 volt DC supply but the cable between the computers has a bunch of pins for battery charging and the like. The last one I had just for fun stuck a 486DX4 100 in it and ran Windows 98, the integrated track ball mouse is a standard deal on military systems.