RAR archive from IBM, around 1.54 MB, carrying a ROME design at revision 3.5 according to its name, likely an earlier schematic issue than the 4.0 set. The name does not say which ThinkPad model uses this board, so confirm it from the document title pages. Technicians rely on such drawings to locate test points, follow power sequencing and diagnose shorted rails. Since revisions 3.5 and 4.0 may differ in component values and placement, compare the revision marked on the PCB before relying on any detail.
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.