RAR archive for the IBM ThinkPad 600 and 600X series, a pair of older business notebooks covered together in roughly 4 MB of material. The name does not state the document type, so extract the package with WinRAR or 7-Zip and inspect what it holds. Such files are typically used to trace power circuits, identify components and locate measurement points on vintage ThinkPad boards. Make sure the system board part number matches the model covered, since the 600 and 600X used different mainboards.
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 @alischematics. 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.