So I've had my 2008 C70 for about a month. Owners manual identifies a 12 volt socket in the rear seat area; I can't find it. However, I did find a hole with a keyed "lock" under the left rear seat on the riser. I cannot find any reference to this lock and it's function. Can someone enlighten me on both issues? Thanks

 

So it turns out the lock is for the trunk; in the event the battery is dead, it opens the trunk using the blade key in the remote fob. Solved with the help of regtor on swedespeed C70 forum.

 

Often pictures also help to identify things. Glad you got this mystery solved!