RAR archive for project M38 at the DVT stage, dated 111605 in the name, with document number 051-6949 revision R09. The 051-xxxx format matches the numbering Apple uses for schematics, and DVT refers to design validation test, a pre-production build stage. At 2.63 MB it likely holds a full schematic set for tracing power rails, checking the SMC and charging circuits and finding test points. Since DVT drawings can differ from shipping boards, verify the 820 number on the PCB before relying on 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 @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.