RAR archive identified only by Apple board number 820-2052. The name gives no schematic number, revision or content description, but the 1.51 MB size is consistent with a full schematic PDF, possibly with extra documents. Apple uses 820- numbers for its printed circuit boards, and that number is normally silkscreened on the PCB, which makes matching straightforward. Open it with 7-Zip or WinRAR to see what is inside, then use it for rail tracing and component identification once the board is confirmed to match.
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 @Mac_Shematic_Santale. 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.