EFI firmware archive for the Apple MacBook Air A1370 logic board 820-2796, project K99, marked DVT, which refers to a design validation test build of the main logic board. The RAR is 2.12 MB and is meant for reprogramming the boot ROM on a board that stays dark or loops at power-on. Flash it with an SPI programmer after dumping the existing chip. Compare the 820 number silkscreened on your board, since Apple reuses model numbers across several logic board generations.
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 @biosarchive. 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.
Back up your own chip before writing any dump, and match the full board number and revision. Flashing guide →