Where is the write-protect switch/screw/jumper on the Samsung Chromebox?

I have a Samsung Series 3 Chromebox, model number XE300M22-B01US, manufactured December 2012.

I would like to put coreboot on it so I can single-boot Linux without ChromeOS pulling the sad face at startup. I tried to flash it but coreboot reported that the BIOS is write protected.

According to this page the jumper/screw is "between the Battery and Ram" except the Chromebox doesn't have a battery and I can't see anything around the RAM area.

Does anyone know where the write-protect screw/jumper/switch is?

Have a look at this picture from the Chromium mailing list: https://groups.google.com/a/chromium.org/forum/#!msg/chromium-os-discuss/P64GQOQNZMw/V0nPeZslQrYJ

You will see this when you have opened the case, opened three screws inside, disconnected some connectors and pulled out the mainboard. Then on the back of the mainboard there will be the jumper as shown on the picture.