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Just go and buy a Kershaw Chive. I use mine for letter opening all the time and it goes over real well at the office. Has a fun assisted opener action. Ideal letter opener if you ask me. And cheap, to boot.
1 15/16" blade. Very pocketable, and pointy, pointy, pointy.
Plus, it's got a frame lock. A frame lock in an itty, bitty, little knife.... how cool is that?!