i read it is tied to the io9 board, and that there is a sticker at the back of the computer - but unfortunately there is none. The tools like ifconfig post infos, but no mac-address either. In system-manager: about htis system, I only get a serial number.
The way you can do this is enable DHCP/BOOTP for the IP35 - then watch the logs on your DHCP server and see the MAC that way.
I just had to do this to find the MAC for my new Fuel... I was using booterizer, which acts as a bootp server and so I let the Fuel try to connect and was able to grab the MAC address right from the server logs.