ok here is another strange one.
i have a few cheap lock backs all the same knife from frost cutlery . in the midel of the lock notch on the blade ther is a small bump. the lock bar sits rite on top of this bump when open. this positon creates two small voids under the lock bar inbetween it and the blades lock notch.
here is a pic in case my description is not clear

http://img205.exs.cx/img205/7311/dsc014785pk.jpg

is this feture there so that if dirt gets in there it has some where to go so that it wont interfeer with the lock?

...justin

That would be my guess. Most lockback designs I've seen have the mating faces of the lock bar and notch ground at an angle to each other to create a space in that same location. The components in your knife appear to be stamped out from relatively soft materials with no square edges so the treatment of the lock notch just follows that direction...