@fennix @rc2014 it is the write project jumper for the EEPROM. The badge checks for an I2C EEPROM when you plug a hexpansion and can load a tiny ( about 1kB in this case) bit of code from it. That code can configure the main storage, make it read only or even chain load more code. To update that "boot sector" EEPROM you must short the header. The location of the header was certainly chosen based on the old write protect switch.