This is likely a kenko-fude (mixed-hair brush) made with horse hair, with a brush head approximately 5.8 cm long and 1.1 cm in diameter, making it a slightly large brush. I believe it's a brush purchased over 40 years ago from Bumbundo, a calligraphy supply store in Tokyo. It has a brown shaft and the slightly stiff bristles are arranged with a slight offset at the tip, allowing for balanced and powerful lines. Although it's a well-used brush, it can produce lines with a variety of expressions, from strong and thick to faded, depending on how much ink is loaded. This brush is suitable for writing the Kaisho script of the Six Dynasties period or powerful poetry and document works. I would like to offer it to someone looking for a brush they can use without hesitation. Thank you for looking.