Archive named only after the Sony MS01 project, 1.15 MB, with no board number or revision in the name. Judging by its size and related files, it likely holds the same schematic set associated with board MBX-143, but verify after extracting. Schematics like this are opened in a PDF viewer and used to trace power rails, follow signals between chips and find test points. Compare the board number on your PCB with the drawing title block before relying on component values or connector pinouts.
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 @generalschematics. 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.