Copy of the repair package for Apple logic board 820-00840 revision A, stored as a 4.85 MB RAR archive. Its size matches other files with the same name, which points to a duplicate upload. The content is not named, though a schematic set is the most probable. Technicians rely on these documents to follow power sequencing, identify components on a shorted rail and verify signal paths. Make sure the PCB reads 820-00840 with revision A before applying any values from it.
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 @cyberlanelectonik. 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.