Yoshihiko Shirakura(Japanese Shunga of Kuniyoshi,
2012, Heibonsha Ltd., Tokyo)
dates this series to 1854-1860, but OferShagan (Japanese Erotic Art, 2013, Thames &
Hudson, London)
dates the series to 1838.Each page is approximately 10 by 7¼
inches or 25.5 by 18.5 centimeters, a size known as ôban.