While I did not watch the show, I did notice that there is an ongoing discussion about this on BladeForums:

http://www.bladeforums.com/forums/showthread.php?t=435403

Last I saw, no one there is certain what kind of knife it was, but if anyone can figure it out -- the people there can.
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When you step out that door in the morning you never really know what you're going to encounter.