Archive in RAR format, 1.95 MB, carrying the identifier 3CESL-RH-01 plus a (1) duplicate marker, which hints at a second copy or alternate variant of a similarly named package. The name does not say what device it serves or whether it contains firmware, diagrams or board data. Unpack it and check the contents before use. Compare it with the other 3CESL-RH-01 file, since the sizes differ slightly. Always check the PCB marking against the label, and back up any SPI chip before reprogramming 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.