Wafer lock.
Double Sided Convenience key, which means the cuts are on both sides of the keys, and are exactly the same.
Wafer locks use thin discs contained entirely in the plug\core of the lock, which are spring loaded. When no key is inserted, they fire out to bind into the housing to prevent turning.
When the incorrect key is inserted, some wafers will be out too far, and some will be depressed too far, causing the other end of the wafer to bind on the other side of the core. (6 oclock, rather than 12 oclock)
Due to the way these locks work, the housing of the lock will have two channels running the entire length that the wafers are free to move into, when a key is inserted, or without. Because the wafer can be above the shearline on the top OR bottom of the plug, an unrestricted plug can be turned 180 degrees and the key removed.
A lot of cam locks on lockers and filing cabinets use this feature, so they can be 'locked open'.
That is exactly what this fire chest has. A double sided convenience key cam lock, with a 180 degree function, allowing it to be locked open, or locked closed.
Is that what you were wondering?
Google resulted in a youtube video.
http://au.youtube.com/watch?v=QOFW9-SB-yM