Apple EFI firmware for logic board 820-3208, revision A, supplied with the BIOS lock removed, so the firmware password should no longer be present. The 8 MB binary fits a 64 Mbit SPI ROM. Apple's 820 number marks the specific logic board, so check the silkscreen for the same number and revision before flashing. Write it with an SPI programmer, ideally using clip or off-board reading first to save the original ROM, since that copy contains the serial number and machine-specific data.
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 @lappysan. 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 →