RAR archive called R13, 4.97 MB, whose name gives no brand, board number or document type. The same-sized copies elsewhere in the collection suggest a widely shared file, perhaps a schematic or firmware package for a board using that code. Extract it with WinRAR or 7-Zip and identify the platform from the documents inside. Compare the board number and revision on the PCB with the contents before tracing rails or flashing, and always save the original SPI chip contents with a programmer before writing anything.
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 @hrtechno. 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.