A Beginners Discussion on Japanese Sword Valuation

I was recently asked by a new Japanese Sword tyro what determines value. Since we have many new collectors here I thought it would be a good topic. Age, attribution, condition, and provenance are all factors.
Age: Older is not always better. Many collectors consider the Nanboku-chō Period spanning from 1336 to 1392 as the Golden Age of sword making. But, there were standout smiths from every period. Furthermore, some collectors are partial to swords from other periods; Kamakura, Nanbokucho, Muromachi, Shinto, Shin-shinto, Gendai. When we hear the term Koto (old) in swords it refers to swords from the Kamakura, Nanbokucho and Muromachi Period. Older swords are typically more valuable in general, but there are many other factors to consider.
Attribution: This is one of the most important factors to consider. After all, nihonto (traditional made Japanese swords) are historical artifacts, so it is important to know who made the sword. This is also where learning and knowledge can pay off. Kantei (attribution) is where we have the most fun in sword collecting. Sometimes it is easy because the sword is signed. Then, it is just confirming the signature. When the sword is mumei (unsigned), or osuriage (tang cut losing signature), collectors must rely on their own knowledge, or that of experts. Organizations like the NBTHK authenticate and paper swords. Of course, a papered sword adds to value. But, not all smiths are equal. Sometimes, an unsigned sword attributed to an important smith is far more valuable than a signed and papered sword by an average smith. One can also forgive certain flaws with swords made by an important smith.
Condition: Any collector wants to avoid swords with fatal flaws such as hagire (transverse crack), but other flaws can greatly affect value. Flaws such as ware (openings in forging), fukure (blister) or nio-gire (interrupted temper line) can greatly detract from value. Everybody wants a perfect Koto katana by an important smith, but they are very tough to come by and can be very expensive as a result.
Provenance: Collectors like a good story. Provenance generally refers to the traceable history of a particular sword. For example, swords once possessed by Daimyo, or famous Samurai, command much higher values. It is human nature to want something other people have valued through history. People will also pay more to buy a sword from a certain dealer. There is a comfort factor, but it is more than that. Photography, research, dealer appreciation… all come into play.