Kaiken 懐剣, sometimes referred to as a Tekken
This Kaiken is a copy of an original Edo period item that was sold on a Japanese auction in 2021.
Kaiken are used to aid and assist in delivering a more powerful strike in Jujutsu kata.
These were normally carried in the kimono sleeve or hidden inside the front of the jacket.
There are a number of different designs, but this one has three protruding tapered spikes.