What is Kesho in Japanese Katana terminology?

The term "Kesho" (化粧, けしょう) refers to a specific pattern of file marks (Yasurime) on a Japanese sword, particularly near the collar (Habaki-moto). This pattern combines the "Kiri" and "Sujikai" file marks. Initially, the file marks on the tang (Nakago) of the sword served a practical purpose, preventing the sword from easily slipping out of the handle. However, in the early Edo period, swordsmiths began to incorporate designs into the file marks to enhance the aesthetic appeal of the tang. As a result, this type of file mark is not found on old swords (Koto), but is limited to new swords (Shinto) and newer swords (Shinshinto).