An archive of repair files for Apple hardware (board 820-2828). Shared as “820-2828 820-2828-A (BVD)(PK).rar” — a .rar file, 118 KB.
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 @pkbiosbdv. 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.
7-ZipWinRARThe Unarchiver (macOS)