Archive tied to Apple logic board 820-00138 from the MacBook Pro A1398, marked read OK, which points to a firmware dump read from the board's flash chip. Apple uses the 820-xxxxx pattern for logic board part numbers, and the exact number and suffix printed on the PCB should match before use. A dump like this is normally written back with an SPI programmer to recover a dead board. Keep a backup of the original chip, since serial and configuration data held in it differ between machines.
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 @CLRINDORE. 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.