This is a very unusual 0-kozuka. It was made by the sword smith, Shigenobu of Tamba. Shigenobu worked around the early 1900’s in Tamba Province. He was a student of Shigehiro. The kozuka almost has a Higo feel to it.
What makes it especially interesting is that instead of a normal ko-gatana blade, it has a blade made in the form of a functioning saw. Aside from the ability to remove the occasional digit, its day to day uses for a Samurai are somewhat perplexing. Perhaps it was on a wakizashi owned by a craftsman/merchant. On the other hand, many poorer Samurai made extra money by making wooden articles such as parasols or bird and insect cages. It would have been very handy for either of those professions.