Small RAR archive, 174 KB, labelled M57 DVT MLB, where MLB means main logic board and DVT means the Design Validation Test build stage. The name gives no brand or device and does not list the contents, so extract it with WinRAR or 7-Zip to see whether it holds a schematic or boardview. Engineering-stage files can differ from production boards, so compare component placement and values with the real PCB. Check the board number and revision 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 @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.
7-ZipWinRARThe Unarchiver (macOS)