The first three bytes of the MAC address are the vendor id:
B827EB = Raspberry Pi Foundation
(From: http://www.coffer.com/mac_find/ )
The final three (of the six bytes) is the last three bytes of the Raspberry Pi Serial number. As this only allows sixteen million presumably the Raspberry Pi Foundation may, eventually, need more than one vendor id...
If the interface is 'eth0' then the MAC address is in:
The Serial number is (the last line) in:
and seems to be sixteen bytes.
Note that on the Model B 2 information is displayed for each of the four CPUs. The same process works for the Model Zero (and the Model A(+)), including the MAC address stuff if an ethernet card is added.
'MAC address' on Wikipedia
Back to Raspberry Pi Page