Samsung firmware image, a 3.88 MB raw binary with SKR8503 and sos in the name; the meaning of those tokens is not stated, so the target model is not clear from the file itself. Raw .bin dumps are written to an SPI flash chip using a hardware programmer. Check that the file size fits the flash on your board, as an image that does not match the chip capacity will not write correctly. Always read and keep a backup of the original chip contents before flashing anything unfamiliar.
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 @led_software. Enginerys does not host this file.
How to open a .bin file
A raw, byte-for-byte image of a flash chip: the main BIOS / UEFI, the embedded-controller (EC) firmware, or both.
Back up your own chip before writing any dump, and match the full board number and revision. Flashing guide →