RAR package of 1.05 MB covering the IBM ThinkPad X31 ultraportable. It is smaller than a ZIP archive listed for the same model, which suggests different or fewer files inside. The name gives no board number, revision or content type, but such archives usually hold the system board schematic. It is used for tracing power rails, finding test points and isolating shorted parts. Check the board revision on the PCB before trusting component values.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @IT_SERVICE_WORLD. Enginerys does not host this file.
How to open a .rar file
Compressed archive — the usual wrapper for a schematic + boardview pair or a BIOS + EC set.
7-ZipWinRARThe Unarchiver (macOS)