After having reviewed many NBTHK papers in my current quest for a pre-Edo tachi, I've noticed many examples of papers that list "1. Katana" and others that list "1. Tachi".  However, I haven't been able to figure out what causes the NBTHK to paper a blade as one versus the other, *except* that I noticed virtually all blades from the late Edo period or after seem to be papered as katana, not tachi.   But I've seen many blades from 1200s, 1300s, and beyond that are papered as tachi or as