Note – a lot more information has become available since I first wrote this one!
This figure is the Japanese silver crucian carp (or Langsdorf’s Goldfish, or Ginbuna in Japan), Carassius langsdorfii (according to Fishbase; earlier sources refer to it as the subspecies Carassius auratus langsdorfii ), stamped number 16 and listed as figure 1 from the Book 2 series, second.