I'm starting to think that gear drops are dependent on the area where you break the boxes.
The following boxes only drop mats, yet look the same as every other box, and the very same box has given me a Skelly Mask twice.
See screenshots (chat log):
http://i52.tinypic.com/z4q9y.png
http://i53.tinypic.com/2ntzd4l.png
Also I got a poison atomizer in a poison wolvers den. I have no screenshot of getting it though.
I think this also applies to tokens.
Anyone got any more evidence to support my theory?
I've gotten a shocking edge in a Power Plant stage in T1.