Small 99.8 KB RAR archive named QT6B, apparently a variant of the QT6 board design. The name gives no maker, board number, revision or document type, so the contents must be inspected after extraction. At this size it most likely holds a boardview or a compact data file rather than a full schematic, but that is unconfirmed. Check the identifier on the motherboard silkscreen and compare it with the extracted files before using them to locate parts or test points.
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.