From what I've discovered, it must be a Japanese Lacquer Brush. Traditionally these are made from the hair of pearl divers, "selected as the finest and densest

From what I've discovered, it must be a Japanese Lacquer Brush. Traditionally these are made from the hair of pearl divers, "selected as the finest and densest fibre."[1] Another reference I found quotes that "They say that the salt strengthens the hair"[2] [1] http://spitalfieldslife.com/2012/01/12/pedro-da-costa-felgueiras-lacquer-paint-specialist-japanner/ http://spitalfieldslife.com/2012/01/12/pedro-da-costa-felgue... [2] https://www.nippon.com/en/views/b02309/ https://www.nippon.com/en/views/b02309/