RAR archive of 1.05 MB named 331-1-4-01-R20, with no brand or model attached. The R20 suffix may indicate revision 2.0, but the name does not confirm it, nor does it say what type of document is inside. After extracting, identify whether it is a schematic, a boardview or a binary dump, and open it with a PDF reader, a boardview viewer or programmer software as appropriate. Always compare the code with the markings on the actual board.
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)