Rare Japanese Ainu Sword

Rare Japanese sword probably of Ainu origin. The Ainu, also called Utari, are an indigenous people from Japan whose last members live in the north of the country, on the island of Hoakkaidō. The koshirae consists of a scabbard and a wooden handle decorated with scarifications and adorned with deer antler mounts as well as decorative motifs in braided plant fibres. A stamped metal kozuka is inserted into the scabbard. The forged steel blade is triangular and quite rustic, not using the usual shapes of Japanese swords.
Japan second half of the 19th century.
Note: the blade has not been disassembled.
For a very close but shorter model, see the exhibition Utari: Ainu, Aboriginal Peoples of Japan The collection of Joseph G. Gerena, Patrick and Ondine Mestdagh Gallery Photo attached