http://www.nij.gov/nij/pubs-sum/183652.htm


I think that this pdf has quite solid description of testing procedures etc.

As far as mail goes - hard to know for sure, but it quite probably wouldn't be practical for such applications.

It most certainly wouldn't stop any bullets of decent energy, protection against spears and stuff is hardly relevant, and few good kg of clanging iron probably isn't considered worth it for knives.

But I'm pretty sure that there are some mail supplemented vest around.