This kaiken, or dagger, is sharp on one edge and has a wood handle with a bone inlay. There are three nails on each side of the handle joining the wood to the blade, which is fairly rusted with age.
A kaiken is an 8-10 inch long, single or double bladed dagger without ornamental fittings housed in a plain mount, formerly carried by men and women of the samurai class. It was useful for self-defense indoors where the long katana (sword) was inconvenient. Women carried them in their kimono either in a pocket-like fold or in the sleeve for self-defense or for ritual suicide. When a samurai woman married, she was expected to carry a kaiken with her when she went to her husband's house to live.