Jackknife, thanks for your input regarding the term "clasp knife." The photos posted here illustrate the concept very well, and agree with you that the term is an old one, even antiquated you could truthfully say. As for its status as a weapon I guess it comes down to someone using whatever knife they own to get the job at hand done. I suspect that most older folding knives were larger than most of today's pocket knives. Of course, many of us have "pocket knives" that are quite a bit larger than pen knives are or were, too!
And nobody much sharpens a goose feather to use it for a pen these days, either.
